Document:

EX-10.3

 Exhibit 10.3 

PRIVATE PLACEMENT WARRANTS PURCHASE AGREEMENT 

THIS PRIVATE PLACEMENT WARRANTS PURCHASE AGREEMENT, dated as of ____________, 2021 (as it may from time to time be amended and including all
exhibits referenced herein, this “Agreement”), is entered into by and between M3-Brigade Acquisition III Corp., a Delaware corporation (the “Company”), M3-Brigade Sponsor III LP, a Delaware limited partnership (the “Sponsor”) and Cantor Fitzgerald & Co., the representative of the underwriters (the “Representative”, and,
together with the Sponsor, the “Purchasers” and, each, a “Purchaser”). 
 WHEREAS, the Company intends to
consummate an initial public offering of the Company’s units (the “Public Offering”), each unit consisting of one share of the Company’s Class A common stock, par value $0.0001 per share (each, a
“Share”), and one-third of one redeemable warrant. Each whole warrant entitles the holder to purchase one Share at an exercise price of $11.50 per Share. The Purchasers have agreed to purchase
an aggregate of 7,046,667 warrants (the “Private Placement Warrants”), each Private Placement Warrant entitling the holder to purchase one Share at an exercise price of $11.50 per Share. The Sponsor has agreed to purchase 5,380,000
Private Placement Warrants and the Representative has agreed to purchase 1,666,667 Private Placement Warrants. 
 NOW THEREFORE, in
consideration of the mutual promises contained in this Agreement and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties to this Agreement hereby, intending legally to be bound, agree as
follows: 
 AGREEMENT 

Section 1. Authorization, Purchase and Sale; Terms of the Private Placement Warrants. 

A. Authorization of the Private Placement Warrants. The Company has duly authorized the issuance and sale of the Private Placement
Warrants to the Purchasers. 
 B. Purchase and Sale of the Private Placement Warrants. 

On the date of the consummation of the Public Offering and concurrently with the consummation thereof, or on such earlier time and date as may
be mutually agreed by the Purchasers and the Company (the “Initial Closing Date”), the Company shall issue and sell to the Purchasers, and the Purchasers shall purchase from the Company, 7,046,667 Private Placement Warrants at a
price of $1.50 per Private Placement Warrant for an aggregate purchase price of $10,570,000 (the “Purchase Price”). The Purchase Price shall be paid by wire transfer of immediately available funds to the Company in accordance with
the Company’s wiring instructions at least one business day prior to the date of effectiveness of the registration statement on Form S-1 (File No.333-256017) filed in connection with the Public Offering.
On the Initial Closing Date, the Company, shall either, at its option, deliver a certificate evidencing the Private Placement Warrants purchased by the Purchasers on such date duly registered in the Purchasers’ names to each of the Purchasers,
or effect such delivery in book-entry form. 

 C. Terms of the Private Placement Warrants. 

(i) The Private Placement Warrants shall have their terms set forth in a Private Warrant Agreement to be entered into by the Company and a
warrant agent, in connection with the Public Offering (a “Private Warrant Agreement”). 
 (ii) At or prior to the time of
the Initial Closing Date, the Company and the Purchasers shall enter into a registration and stockholder rights agreement (the “Registration and Stockholder Rights Agreement”) pursuant to which the Company will grant certain
registration rights to the Purchasers relating to the Private Placement Warrants and the Shares underlying the Private Placement Warrants. 

Section 2. Representations and Warranties of the Company. As a material inducement to the Purchasers to enter
into this Agreement and purchase the Private Placement Warrants, the Company hereby represents and warrants to each of the Purchasers (which representations and warranties shall survive each Closing Date) that: 

A. Organization and Corporate Power. The Company is a corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware and is qualified to do business in every jurisdiction in which the failure to so qualify would reasonably be expected to have a material adverse effect on the financial condition, operating results or assets of the Company.
The Company possesses all requisite corporate power and authority necessary to carry out the transactions contemplated by this Agreement and the Private Warrant Agreement. 

B. Authorization; No Breach. 

(i) The execution, delivery and performance of this Agreement and the Private Placement Warrants have been duly authorized and approved by the
Company as of each Closing Date. This Agreement constitutes a valid and binding obligation of the Company, enforceable in accordance with its terms. Upon issuance in accordance with, and payment pursuant to, the terms of the Private Warrant
Agreement and this Agreement, the Private Placement Warrants will constitute valid and binding obligations of the Company, enforceable in accordance with their terms. 

  
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 (ii) The execution and delivery by the Company of this Agreement and the Private Placement
Warrants, the issuance and sale of the Private Placement Warrants, the issuance of the Shares upon exercise of the Private Placement Warrants and the fulfillment of, and compliance with, the respective terms hereof and thereof by the Company, do not
and will not as of each Closing Date (a) conflict with or result in a breach of the terms, conditions or provisions of, (b) constitute a default under, (c) result in the creation of any lien, security interest, charge or encumbrance
upon the Company’s capital stock or assets under, (d) result in a violation of, or (e) require any authorization, consent, approval, exemption, action, notice, declaration or filing, in each case, by or to any court or administrative
or governmental body or agency pursuant to the certificate of incorporation or the bylaws of the Company (in effect on the date hereof or as may be amended prior to completion of the contemplated Public Offering), or any material law, statute, rule
or regulation to which the Company is subject, or any agreement, order, judgment or decree to which the Company is subject, except for any filings required after the date hereof under federal or state securities laws. 

C. Title to Securities. Upon issuance in accordance with, and payment pursuant to, the terms hereof and the Private Warrant Agreement,
the Placement Warrants will be duly and validly issued and the Shares issuable upon exercise of the Private Placement Warrants will be duly and validly issued, fully paid and nonassessable. On the date of issuance of the Placement Warrants, the
Shares issuable upon exercise of the Placement Warrants shall have been reserved for issuance. Upon issuance in accordance with, and payment pursuant to, the terms hereof and the Private Warrant Agreement, the Purchasers will have good title to the
Private Placement Warrants and the Shares issuable upon exercise of such Private Placement Warrants, free and clear of all liens, claims and encumbrances of any kind, other than (i) transfer restrictions hereunder and under the other agreements
contemplated hereby, (ii) transfer restrictions under federal and state securities laws, and (iii) liens, claims or encumbrances imposed due to the actions of the Purchasers. 

D. Valid Issuance. The total number of shares of all classes of capital stock which the Company has authority to issue is 550,000,000
shares of common stock (which consist of 500,000,000 shares of the Company’s Class A Common Stock and 50,000,000 shares of the Company’s Class B common stock, par value $0.0001 per share (the “Class B
Common Stock”)) and 1,000,000 shares of the Company’s preferred stock, par value $0.0001, per share (the “Preferred Stock”). As of the date hereof, the Company has issued and outstanding no shares of Class A
Common Stock, 7,187,500 shares of Class B Common Stock (of which up to 937,500 shares are subject to forfeiture as described in the Registration Statement) and no shares of Preferred Stock. All of the issued shares of capital stock of the
Company have been duly authorized, validly issued, and are fully paid and non-assessable. 
 E.
Governmental Consents. No permit, consent, approval or authorization of, or declaration to or filing with, any governmental authority is required in connection with the execution, delivery and performance by the Company of this Agreement or
the consummation by the Company of any other transactions contemplated hereby. 

  
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 Section 3. Representations and Warranties of the Purchasers.
As a material inducement to the Company to enter into this Agreement and issue and sell the Private Placement Warrants to the Purchasers, each of the Purchasers hereby represents and warrants to the Company (which representations and warranties
shall survive each Closing Date) that: 
 A. Organization and Requisite Authority. The Purchasers possess all requisite power and
authority necessary to carry out the transactions contemplated by this Agreement. 
 B. Authorization; No Breach. 

(i) This Agreement constitutes a valid and binding obligation of the Purchaser, enforceable in accordance with its terms, subject to
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and other laws of general applicability relating to or affecting creditors’ rights and to general equitable principles (whether considered in a proceeding in equity or
law). 
 (ii) The execution and delivery by the Purchaser of this Agreement and the fulfillment of and compliance with the terms hereof by
the Purchaser does not and shall not as of each Closing Date conflict with or result in a breach by the Purchaser of the terms, conditions or provisions of any agreement, instrument, order, judgment or decree to which the Purchaser is subject that
would materially impact its ability to perform its obligations hereunder. 
 C. Investment Representations. 

(i) The Purchaser is acquiring the Private Placement Warrants and, upon exercise of the Private Placement Warrants, the Shares issuable upon
such exercise (collectively, the “Securities”), for the Purchaser’s own account, for investment purposes only and not with a view towards, or for resale in connection with, any public sale or distribution thereof. 

(ii) The Purchaser is an “accredited investor” as such term is defined in Rule 501(a)(3) of Regulation D of the Securities Act of
1933, as amended (the “Securities Act”). 
 (iii) The Purchaser understands that the Securities are being offered and will
be sold to it in reliance on specific exemptions from the registration requirements of the United States federal and state securities laws and that the Company is relying upon the truth and accuracy of, and the Purchaser’s compliance with, the
representations and warranties of the Purchaser set forth herein in order to determine the availability of such exemptions and the eligibility of the Purchaser to acquire such Securities. 

(iv) The Purchaser did not enter into this Agreement as a result of any general solicitation or general advertising within the meaning of Rule
502(c) under the Securities Act. 
 (v) The Purchaser has been furnished with all materials relating to the business, finances and
operations of the Company and materials relating to the offer and sale of the Securities which have been requested by the Purchaser. The Purchaser has been afforded the opportunity to ask questions of the executive officers and directors of the
Company. The Purchaser understands that its investment in the Securities involves a high degree of risk and it has sought such accounting, legal and tax advice as it has considered necessary to make an informed investment decision with respect to
the acquisition of the Securities. 

  
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 (vi) The Purchaser understands that no United States federal or state agency or any other
government or governmental agency has passed on or made any recommendation or endorsement of the Securities or the fairness or suitability of the investment in the Securities by the Purchaser nor have such authorities passed upon or endorsed the
merits of the offering of the Securities. 
 (vii) The Purchaser understands that: (a) the Securities have not been and are not being
registered under the Securities Act or any state securities laws, and may not be offered for sale, sold, assigned or transferred unless (1) subsequently registered thereunder or (2) sold in reliance on an exemption therefrom; and
(b) except as specifically set forth in the Registration and Stockholder Rights Agreement, neither the Company nor any other person is under any obligation to register the Securities under the Securities Act or any state securities laws or to
comply with the terms and conditions of any exemption thereunder. While the Purchaser understands that Rule 144 under the Securities Act is not available for the resale of securities initially issued by shell companies (other than business
combination related shell companies) or issuers that have been at any time previously a shell company, the Purchaser understands that Rule 144 includes an exception to this prohibition if the following conditions are met: (i) the issuer of the
securities that was formerly a shell company has ceased to be a shell company; (ii) the issuer of the securities is subject to the reporting requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended (the
“Exchange Act”); (iii) the issuer of the securities has filed all Exchange Act reports and material required to be filed, as applicable, during the preceding 12 months (or such shorter period that the issuer was required to file
such reports and materials), other than Form 8-K reports; and (iv) at least one year has elapsed from the time that the issuer filed current Form 10 type information with the SEC reflecting its status as
an entity that is not a shell company. 
 (viii) The Purchaser has knowledge and experience in financial and business matters, understands
the high degree of risk associated with investments in the securities of companies in the development stage such as the Company, is capable of evaluating the merits and risks of an investment in the Securities and is able to bear the economic risk
of an investment in the Securities in the amount contemplated hereunder for an indefinite period of time. The Purchaser has adequate means of providing for its current financial needs and contingencies and will have no current or anticipated future
needs for liquidity which would be jeopardized by the investment in the Securities. The Purchaser can afford a complete loss of its investment in the Securities. 

Section 4. Conditions of the Purchasers’ Obligations. The obligations of the Purchasers to purchase and
pay for the Private Placement Warrants are subject to the fulfillment, on or before each Closing Date, of each of the following conditions: 

A. Representations and Warranties. The representations and warranties of the Company contained in Section 2 shall be true and
correct at and as of such Closing Date as though then made. 

  
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 B. Performance. The Company shall have performed and complied with all agreements,
obligations and conditions contained in this Agreement that are required to be performed or complied with by it on or before such Closing Date. 

C. No Injunction. No litigation, statute, rule, regulation, executive order, decree, ruling or injunction shall have been enacted,
entered, promulgated or endorsed by or in any court or governmental authority of competent jurisdiction or any self-regulatory organization having authority over the matters contemplated hereby, which prohibits the consummation of any of the
transactions contemplated by this Agreement or the Private Warrant Agreement. 
 D. Private Warrant Agreement and Registration and
Stockholder Rights Agreement. The Company shall have entered into a Private Warrant Agreement with a warrant agent and the Registration and Stockholder Rights Agreement, each on terms satisfactory to each of the Purchasers. 

E. Corporate Consents. The Company shall have obtained the consent of its Board of Directors authorizing the execution, delivery and
performance of this Agreement and the Private Warrant Agreement and the issuance and sale of the Private Placement Warrants hereunder. 

Section 5. Conditions of the Company’s Obligations. The obligations of the Company to the Purchasers
under this Agreement are subject to the fulfillment, on or before each Closing Date, of each of the following conditions: 
 A.
Representations and Warranties. The representations and warranties of each of the Purchasers contained in Section 3 shall be true and correct at and as of such Closing Date as though then made. 

B. Performance. Each of the Purchasers shall have performed and complied with all agreements, obligations and conditions contained in
this Agreement that are required to be performed or complied with by the Purchaser on or before such Closing Date. 
 C. Corporate
Consents. The Company shall have obtained the consent of its Board of Directors authorizing the execution, delivery and performance of this Agreement and the Private Warrant Agreement and the issuance and sale of the Private Placement Warrants
hereunder. 
 D. No Injunction. No litigation, statute, rule, regulation, executive order, decree, ruling or injunction shall have
been enacted, entered, promulgated or endorsed by or in any court or governmental authority of competent jurisdiction or any self-regulatory organization having authority over the matters contemplated hereby, which prohibits the consummation of any
of the transactions contemplated by this Agreement or the Private Warrant Agreement. 
 E. Private Warrant Agreement. The Company
shall have entered into a Private Warrant Agreement with a warrant agent on terms satisfactory to the Company. 

Section 6. Termination. This Agreement may be terminated at any time after December 31, 2021 upon the
election by either the Company, the Sponsor or the Representative upon written notice to each of the other parties if the closing of the Public Offering does not occur prior to such date. 

  
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 Section 7. Survival of Representations and Warranties. All
of the representations and warranties contained herein shall survive each Closing Date. 
 Section 8.
Definitions. Terms used but not otherwise defined in this Agreement shall have the meaning assigned to such terms in the registration statement on Form S-1 the Company has filed with the Securities
and Exchange Commission under the Securities Act in connection with the Public Offering. 
 Section 9. Miscellaneous. 

A. Successors and Assigns. Except as otherwise expressly provided herein, all covenants and agreements contained in this Agreement by or
on behalf of any of the parties hereto shall bind and inure to the benefit of the respective successors of the parties hereto whether so expressed or not. Notwithstanding the foregoing or anything to the contrary herein, the parties may not assign
this Agreement without the prior written consent of the other parties hereto, other than assignments by the Sponsor to its affiliates (including, without limitation, one or more of its members). 

B. Severability. Whenever possible, each provision of this Agreement shall be interpreted in such manner as to be effective and valid
under applicable law, but if any provision of this Agreement is held to be prohibited by or invalid under applicable law, such provision shall be ineffective only to the extent of such prohibition or invalidity, without invalidating the remainder of
this Agreement. 
 C. Counterparts. This Agreement may be executed simultaneously in two or more counterparts, none of which needs to
contain the signatures of more than one party, but all such counterparts taken together shall constitute one and the same agreement. In the event that any signature is delivered by facsimile transmission or by
e-mail delivery of a “pdf” format data file, such signature shall create a valid and binding obligation of the party executing (or on whose behalf such signature is executed) with the same force and
effect as if such facsimile or “.pdf” signature page were an original thereof. 
 D. Descriptive Headings; Interpretation.
The descriptive headings of this Agreement are inserted for convenience only and do not constitute a substantive part of this Agreement. The use of the word “including” in this Agreement shall be by way of example rather than by
limitation. 
 E. Governing Law. This Agreement shall be deemed to be a contract made under the laws of the State of New York and for
all purposes shall be construed in accordance with the internal laws of the State of New York, without regard to the conflicts of laws principles thereof. 

F. Amendments. This Agreement may not be amended, modified or waived as to any particular provision, except by a written instrument
executed by all parties hereto. 
 [Signature Page Follows] 

 

  
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 IN WITNESS WHEREOF, the parties hereto have executed this Agreement to be effective
as of the date first set forth above. 
  

			
	COMPANY:
	
	M3-BRIGADE ACQUISITION III CORP., a Delaware corporation
		
	By:	 	  

		 	Name: Mohsin Meghji
		 	Title: Executive Chairman of the Board of Directors
	
	PURCHASERS:
	
	M3-BRIGADE SPONSOR III LP, a Delaware limited partnership
	
	By: M3-Brigade Acquisition Partners III. Corp.
		
	By	 	  

	Name: Mohsin Meghji
	Title: Authorized Person
	
	CANTOR FITZGERALD & CO., a [    ]
		
	By	 	      

	Name:
	Title:

 [Signature Page to Private Placement Warrants Purchase Agreement]EX-10.7

 Exhibit 10.7 

, 2021 

M3-Brigade Acquisition III Corp. 

1700 Broadway, 19th Floor 
 New York, NY 10019 

Re: Initial Public Offering 
 Ladies and
Gentlemen: 
 This letter (this “Letter Agreement”) is being delivered to you in accordance with the Underwriting
Agreement (the “Underwriting Agreement”) entered into by and between M3-Brigade Acquisition III Corp., a Delaware corporation (the “Company”), and Cantor
Fitzgerald & Co., as representative (the “Representative”) of the several underwriters (each, an “Underwriter” and collectively, the “Underwriters”), relating to an
underwritten initial public offering (the “Public Offering”), of up to 28,750,000 of the Company’s units (including up to 3,750,000 units that may be purchased to cover over-allotments, if any) (the
“Units”), each comprised of one share of the Company’s Class A common stock, par value $0.0001 per share (the “Class A Common Stock”), and one-third of one redeemable public warrant (each whole public warrant, a “Public Warrant”). Each Public Warrant entitles the holder thereof to purchase one share of Class A Common Stock
at a price of $11.50 per share, subject to adjustment as described in the Prospectus (as defined below). The Units will be sold in the Public Offering pursuant to a registration statement on Form S-1 and
prospectus (the “Prospectus”) filed by the Company with the U.S. Securities and Exchange Commission (the “Commission”) and the Units have been approved for listing on the New York Stock Exchange.
Certain capitalized terms used herein are defined in paragraph 11 hereof. 
 In order to induce the Company and the Underwriters to enter
into the Underwriting Agreement and to proceed with the Public Offering and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, each of M3-Brigade Sponsor
III LP (the “Sponsor”) and the undersigned individuals, each of whom is a member of the Company’s board of directors and/or management team (each of the undersigned individuals, an “Insider” and
collectively, the “Insiders”), hereby agrees with the Company as follows: 
 1. The Sponsor and each Insider agrees
that if the Company seeks stockholder approval of a proposed Business Combination, then in connection with such proposed Business Combination, it, he or she shall (i) vote any shares of Common Stock (as defined below) owned by it, him or her in
favor of any proposed Business Combination and (ii) not redeem any shares of Common Stock owned by it, him or her in connection with such stockholder approval. If the Company seeks to consummate a proposed Business Combination by engaging in a
tender offer, the Sponsor and each Insider agrees that it, he or she will not sell or tender any shares of Common Stock owned by it, him or her in connection therewith. The Company agrees not to enter into a definitive agreement with respect to an
initial business combination without the written consent of the Sponsor. 

 2. The Sponsor and each Insider hereby agrees that in the event that the Company fails to
consummate a Business Combination within 12 months from the closing of the Public Offering, (or up to 24 months, as provided by Section 9.1(c) of the Company’s amended and restated certificate of incorporation (as it may be amended from time to
time, the “Charter”)) or such later period approved by the Company’s stockholders in accordance with the Charter, the Sponsor and each Insider shall take all reasonable steps to cause the Company to (i) cease all
operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem 100% of the shares of Class A Common Stock sold as part of the Units in the Public Offering
(the “Offering Shares”), at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account (as defined below), including interest earned on the
funds held in the Trust Account not previously released to the Company to pay working capital expenses (which interest shall be net of taxes payable and up to $100,000 of interest to pay dissolution expenses), divided by the number of then
outstanding Offering Shares, which redemption will completely extinguish all Public Stockholders’ rights as stockholders (including the right to receive further liquidating distributions, if any), and (iii) as promptly as reasonably
possible following such redemption, subject to the approval of the Company’s remaining stockholders and the Company’s board of directors, liquidate and dissolve, subject in each case to the Company’s obligations under Delaware law to
provide for claims of creditors and other requirements of applicable law. The Sponsor and each Insider agrees to not propose any amendment to the Charter to modify the substance or timing of the Company’s obligation to redeem 100% of the
Offering Shares if the Company does not complete a Business Combination within the required time period set forth in the Charter or with respect to any other material provisions relating to stockholders’ rights or
pre-initial business combination activity, unless the Company provides its Public Stockholders with the opportunity to redeem their Offering Shares upon approval of any such amendment at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in the Trust Account not previously released to the Company to pay
working capital expenses (which interest shall be net of taxes payable and up to $100,000 of interest to pay dissolution expenses), divided by the number of then outstanding Offering Shares. 

The Sponsor and each Insider acknowledges that it, he or she has no right, title, interest or claim of any kind in or to any monies held in
the Trust Account or any other asset of the Company as a result of any liquidation of the Company with respect to the Founder Shares held by it, him or her. The Sponsor and each Insider hereby further waives, with respect to any shares of Common
Stock held by it, him or her, if any, any redemption rights it, he or she may have in connection with (A) the consummation of a Business Combination, including, without limitation, any such rights available in the context of a stockholder vote
to approve such Business Combination, or (B) a stockholder vote to approve an amendment to the Charter to modify the substance or timing of the Company’s obligation to redeem 100% of the Offering Shares if the Company has not consummated a
Business Combination within the time period set forth in the Charter or with respect to any other material provisions relating to stockholders’ rights or pre-initial business combination activity or in
the context of a tender offer made by the Company to purchase Offering Shares (although the Sponsor, the Insiders and their respective affiliates shall be entitled to redemption and liquidation rights with respect to any Offering Shares it or they
hold if the Company fails to consummate a Business Combination within the time period set forth in the Charter). 

  
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 3. During the period commencing on the effective date of the Underwriting Agreement and
ending 180 days after such date, the Sponsor and each Insider shall not, other than as permitted in the Amended and Restated Operating Agreement of the Sponsor, as amended, supplemented or modified, from time to time, without the prior written
consent of the Representative, (i) sell, offer to sell, contract or agree to sell, hypothecate, pledge, grant any option to purchase or otherwise dispose of or agree to dispose of, directly or indirectly, or establish or increase a put
equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules and regulations of the
Commission promulgated thereunder, with respect to, any Units, shares of Common Stock (including, but not limited to, Founder Shares), Public Warrants or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock
owned by it, him or her, (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any Units, shares of Common Stock (including, but not limited to, Founder
Shares), Public Warrants or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock owned by it, him or her, whether any such transaction is to be settled by delivery of such securities, in cash or otherwise, or
(iii) publicly announce any intention to effect any transaction specified in clause (i) or (ii). For the avoidance of doubt, none of the provisions of this Section 3 shall apply for any transactions entered into
in connection with the consummation of an initial Business Combination. 
 4. In the event of the liquidation of the Trust Account upon the
failure of the Company to consummate its initial Business Combination within the time period set forth in the Charter, the Sponsor (which for purposes of clarification shall not extend to any other shareholders, members or managing managers of the
Sponsor) (the “Indemnitor”) agrees to indemnify and hold harmless the Company against any and all loss, liability, claim, damage and expense whatsoever (including, but not limited to, any and all legal or other expenses
reasonably incurred in investigating, preparing or defending against any litigation, whether pending or threatened) to which the Company may become subject as a result of any claim by (i) any third party for services rendered or products sold
to the Company or (ii) any prospective target business with which the Company has entered into a written letter of intent, confidentiality or other similar agreement or Business Combination agreement (a “Target”);
provided, however, that such indemnification of the Company by the Indemnitor (x) shall apply only to the extent necessary to ensure that such claims by a third party or a Target do not reduce the amount of funds in the Trust Account to below
the lesser of (i) $10.10 per Offering Share and (ii) the actual amount per Offering Share held in the Trust Account as of the date of the liquidation of the Trust Account, if less than $10.10 per Offering Share is then held in the Trust Account
due to reductions in the value of the trust assets, less taxes payable, (y) shall not apply to any claims by a third party or a Target which executed a waiver of any and all rights to the monies held in the Trust Account (whether or not such
waiver is enforceable) and (z) shall not apply to any claims under the Company’s indemnity of the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended. In the event that any such
executed waiver by a third party or a Target is deemed to be unenforceable against such third party or Target, the Sponsor shall not be responsible to the extent of any liability for such third-party claims. The Indemnitor shall have the right to
defend against any such claim with counsel of its choice reasonably satisfactory to the Company if, within 15 days following written receipt of notice of the claim to the Indemnitor, the Indemnitor notifies the Company in writing that it shall
undertake such defense. For the avoidance of doubt, none of the Company’s officers or directors will indemnify the Company for claims by third parties, including, without limitation, claims by vendors and prospective target businesses. 

  
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 5. To the extent that the Underwriters do not exercise their over-allotment option to
purchase up to an additional 3,750,000 Units within 45 days from the date of the Prospectus (and as further described in the Prospectus), the Sponsor agrees to forfeit, at no cost, a number of Founder Shares in the aggregate equal to 937,500
multiplied by a fraction, (i) the numerator of which is 3,750,000 minus the number of Units purchased by the Underwriters upon the exercise of their over-allotment option, and (ii) the denominator of which is 3,750,000. The forfeiture will
be adjusted to the extent that the over-allotment option is not exercised in full by the Underwriters so that the Founder Shares will represent an aggregate of 20.0% of the Company’s issued and outstanding shares of Class A Common Stock
after the Public Offering (not including shares of Class A Common Stock underlying the Public Warrants or Private Placement Warrants (as defined below)). The Sponsor further agrees that to the extent that the size of the Public Offering is
increased or decreased, the Company will purchase or sell shares or effect a share repurchase or share capitalization, as applicable, immediately prior to the consummation of the Public Offering in such amount as to maintain the ownership of the
initial shareholders prior to the Public Offering at 20.0% of its issued and outstanding Capital Shares upon the consummation of the Public Offering. In connection with such increase or decrease in the size of the Public Offering, then (A) the
references to 3,750,000 in the numerator and denominator of the formula in the first sentence of this paragraph shall be changed to a number equal to 15% of the number of Public Shares included in the Units issued in the Public Offering and
(B) the reference to 937,500 in the formula set forth in the first sentence of this paragraph shall be adjusted to such number of Founder Shares that the Sponsor would have to surrender to the Company in order for the initial shareholders to
hold an aggregate of 20.0% of the Company’s issued and outstanding shares of Class A Common Stock after the Public Offering (not including shares of Class A Common Stock underlying the Public Warrants or Private Placement Warrants).

 6. The Sponsor and each Insider hereby agrees and acknowledges that: (i) the Underwriters and the Company would be irreparably
injured in the event of a breach by such Sponsor or an Insider of its, his or her obligations under paragraphs 1, 2, 3, 4, 5, 7, 7(b) and 9, as applicable, of this Letter Agreement (ii) monetary damages may not be an adequate remedy for such
breach and (iii) the non-breaching party shall be entitled to injunctive relief, in addition to any other remedy that such party may have in law or in equity, in the event of such breach. 

7. (a) The Sponsor and each Insider agrees that it, he or she shall not Transfer any Founder Shares (or any shares of Class A Common
Stock issuable upon conversion thereof) until the earlier of (A) one year after the completion of the Company’s initial Business Combination and (B) subsequent to the Business Combination, (x) if the closing price of the
Class A Common Stock equals or exceeds $12.00 per share (as adjusted for stock splits, stock dividends, reorganizations, recapitalizations and the like) for any 20 trading days within any 30-trading day
period commencing at least 150 days after the Company’s initial Business Combination or (y) the date on which the Company completes a liquidation, merger, capital stock exchange, reorganization or other similar transaction that results in
all of the Company’s stockholders having the right to exchange their shares of Class A Common Stock for cash, securities or other property (the “Founder Shares Lock-up
Period”). 

  
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 (b) The Sponsor and each Insider agrees that it, he or she shall not Transfer any Private
Placement Warrants (or any share of Class A Common Stock issued or issuable upon the exercise of the Private Placement Warrants), until 30 days after the completion of a Business Combination (the “Private Placement Warrants Lock-up Period”, together with the Founder Shares Lock-up Period, the “Lock-up Periods”). 

(c) Notwithstanding the provisions set forth in paragraphs 7(a) and (b), Transfers of the Founder Shares, Private Placement Warrants and shares
of Class A Common Stock issued or issuable upon the exercise or conversion of the Private Placement Warrants or the Founder Shares that are held by the Sponsor, any Insider or any of their permitted transferees (that have complied with this
paragraph 7(c)), are permitted (i) to the Company’s officers or directors, any affiliate or family member of any of the Company’s officers or directors, any affiliate of the Sponsor or to any members of the Sponsor or any of their
affiliates; (ii) in the case of an individual, by gift to a member of such individual’s immediate family or to a trust, the beneficiary of which is a member of such individual’s immediate family, an affiliate of such individual or to
a charitable organization; (iii) in the case of an individual, by virtue of laws of descent and distribution upon death of such individual; (iv) in the case of an individual, pursuant to a qualified domestic relations order; (v) by
private sales or transfers made in connection with any forward purchase agreement or any financing transaction or similar arrangement or in connection with the consummation of an initial Business Combination at prices no greater than the price at
which each type of security was originally purchased; (vi) in the event of the Company’s liquidation prior to the completion of an initial Business Combination; (vii) by virtue of the laws of the State of Delaware (viii) the
Operating Agreement of the Sponsor, as amended, supplemented or modified, from time to time ; or (ix) in the event of the Company’s liquidation, merger, capital stock exchange or other similar transaction which results in all of the
Company’s stockholders having the right to exchange their shares of Class A Common Stock for cash, securities or other property subsequent to the Company’s completion of an initial Business Combination; provided, however, that in the
case of clauses (i) through (ix), these permitted transferees must enter into a written agreement with the Company agreeing to be bound by the transfer restrictions herein and the other restrictions contained in this Agreement (including
provisions relating to voting, the Trust Account and liquidating distributions). 
 8. The Sponsor and each Insider represents and warrants
that it, he or she has never been suspended or expelled from membership in any securities or commodities exchange or association or had a securities or commodities license or registration denied, suspended or revoked. Each Insider’s
biographical information furnished to the Company (including any such information included in the Prospectus) is true and accurate in all respects and does not omit any material information with respect to the Insider’s background. The Sponsor
and each Insider’s questionnaire furnished to the Company is true and accurate in all respects. The Sponsor and each Insider represents and warrants that: it, he or she is not subject to or a respondent in any legal action for, any injunction, cease-and-desist order or order or stipulation to desist or refrain from any act or practice relating to the offering of securities in any jurisdiction; it, he or she has
never been convicted of, or pleaded guilty to, any crime (i) involving fraud, (ii) relating to any financial transaction or handling of funds of another person, or (iii) pertaining to any dealings in any securities and it, he or she
is not currently a defendant in any such criminal proceeding. 

  
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 9. Except as disclosed in the Prospectus, neither the Sponsor nor any officer, nor any
affiliate of the Sponsor or any officer, nor any director of the Company, shall receive from the Company any finder’s fee, reimbursement, consulting fee, non-cash payments, monies in respect of any
repayment of a loan or other compensation prior to, or in connection with any services rendered in order to effectuate, the consummation of the Company’s initial Business Combination (regardless of the type of transaction that it is), other
than the following, none of which will be made from the proceeds held in the Trust Account prior to the completion of the initial Business Combination: repayment of a loan and advances up to an aggregate of $300,000 made to the Company by the
Sponsor to cover offering-related and organizational expenses; cash compensation to an affiliate of the Sponsor, for any financial advisory, placement agency or other similar investment banking services that such affiliate may provide to our
company, in connection with our initial Business Combination upon the consummation of our initial business combination, and reimbursement to such affiliate for any
out-of-pocket expenses incurred by it in connection with the performance of such services; reimbursement for any reasonable out-of-pocket expenses related to identifying, investigating, negotiating and consummating an initial Business Combination, and repayment of non-interest bearing loans
which may be made by the Sponsor or an affiliate of the Sponsor or certain of the Company’s officers and directors to finance transaction costs in connection with an intended initial Business Combination, provided, that, if the Company does not
consummate an initial Business Combination, a portion of the working capital held outside the Trust Account may be used by the Company to repay such loaned amounts so long as no proceeds from the Trust Account are used for such repayment. Up to
$1,500,000 of such loans may be convertible into warrants of the post-business combination entity at a price of $1.50 per warrant at the option of the lender Such warrants would be identical to the Private Placement Warrants (as defined below),
including as to exercise price, exercisability and exercise period. 
 10. The Sponsor and each Insider has full right and power, without
violating any agreement to which it is bound (including, without limitation, any non-competition or non-solicitation agreement with any employer or former employer), to
enter into this Letter Agreement and, as applicable, to serve as an officer and/or director on the board of directors of the Company and hereby consents to being named in the Prospectus as an officer and/or director of the Company. 

11. As used herein, (i) “Business Combination” shall mean a merger, consolidation, capital stock exchange, asset
acquisition, stock purchase, reorganization or similar business combination, involving the Company and one or more businesses; (ii) “Common Stock” shall mean the Class A common stock and Class B common stock, par
value $0.0001 per share (“Class B Common Stock”); (iii) “Founder Shares” shall mean the 7,187,500 shares of Class B common stock issued and outstanding (up to
937,500 Shares of which are subject to complete or partial forfeiture if the over-allotment option is not exercised by the Underwriters); (iv) “Initial Stockholders” shall mean the Sponsor and any Insider that holds Founder
Shares; (v) “Private Placement Warrants” shall mean the 7,046,667 warrants that the Sponsor and the Representative have agreed to purchase for an aggregate purchase price of $10,570,000, or $1.50 per Private Placement
Warrant, in a private placement transaction that shall occur simultaneously with the consummation of the Public Offering; (vi) “Public Stockholders” shall mean the holders of securities issued in the Public Offering; (vii)
“Trust Account” shall mean the trust fund into which a portion of the net proceeds of the Public Offering and the sale of the Private Placement Warrants shall be deposited; (viii) “Transfer”

  
 6 

 
shall mean the (a) sale of, offer to sell, contract or agreement to sell, hypothecate, pledge, grant of any option to purchase or otherwise dispose of or agreement to dispose of, directly or
indirectly, or establishment or increase of a put equivalent position or liquidation with respect to or decrease of a call equivalent position within the meaning of Section 16 of the Exchange Act, and the rules and regulations of the Commission
promulgated thereunder with respect to, any security, (b) entry into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any security, whether any such transaction is to
be settled by delivery of such securities, in cash or otherwise, or (c) public announcement of any intention to effect any transaction specified in clause (a) or (b); and (ix) “Warrants” shall mean the Private
Placement Warrants and Public Warrants. 
 12. The Company will maintain an insurance policy or policies providing directors’ and
officers’ liability insurance, and each Director shall be covered by such policy or policies, in accordance with its or their terms, to the maximum extent of the coverage available for any of the Company’s directors or officers. 

13. This Letter Agreement constitutes the entire agreement and understanding of the parties hereto in respect of the subject matter hereof and
supersedes all prior understandings, agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter hereof or the transactions contemplated hereby. This Letter Agreement may
not be changed, amended, modified or waived (other than to correct a typographical error) as to any particular provision, except by a written instrument executed by all parties hereto. 

14. No party hereto may assign either this Letter Agreement or any of its rights, interests, or obligations hereunder without the prior
written consent of the other parties. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or title to the purported assignee. This Letter Agreement shall be
binding on the Sponsor and each Insider and their respective successors, heirs and assigns and permitted transferees. 
 15. Nothing in this
Letter Agreement shall be construed to confer upon, or give to, any person or corporation other than the parties hereto any right, remedy or claim under or by reason of this Letter Agreement or of any covenant, condition, stipulation, promise or
agreement hereof. All covenants, conditions, stipulations, promises and agreements contained in this Letter Agreement shall be for the sole and exclusive benefit of the parties hereto and their successors, heirs, personal representatives and assigns
and permitted transferees. 
 16. This Letter Agreement may be executed in any number of original or facsimile counterparts and each of such
counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. 

17. This Letter Agreement shall be deemed severable, and the invalidity or unenforceability of any term or provision hereof shall not affect
the validity or enforceability of this Letter Agreement or of any other term or provision hereof. Furthermore, in lieu of any such invalid or unenforceable term or provision, the parties hereto intend that there shall be added as a

  
 7 

 
part of this Letter Agreement a provision as similar in terms to such invalid or unenforceable provision as may be possible and be valid and enforceable. 

18. This Letter Agreement shall be governed by and construed and enforced in accordance with the laws of the State of New York without giving
effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction. The parties hereto (i) all agree that any action, proceeding, claim or dispute arising out of, or relating in any way
to, this Letter Agreement shall be brought and enforced in the courts of New York City, in the State of New York, and irrevocably submit to such jurisdiction and venue, which jurisdiction and venue shall be exclusive and (ii) waive any
objection to such exclusive jurisdiction and venue or that such courts represent an inconvenient forum. 
 19. Any notice, consent or
request to be given in connection with any of the terms or provisions of this Letter Agreement shall be in writing and shall be sent by express mail or similar private courier service, by certified mail (return receipt requested), by hand delivery
or facsimile transmission. 
 20. This Letter Agreement shall terminate on the earlier of (i) the expiration of the Lock-up Periods or (ii) the liquidation of the Company; provided, however, that this Letter Agreement shall earlier terminate in the event that the Public Offering is not consummated by December 31, 2021;
provided further that paragraph 4 of this Letter Agreement shall survive such liquidation. 
 [Signature Page Follows] 

  
 8 

 
			
	Sincerely,
	
	M3-BRIGADE SPONSOR III LP
	
	By: M3-Brigade Acquisition Partners III Corp.
		
	By:	 	          

		 	Name: Mohsin Meghji
		 	Title: Authorized Person
		
		 	
		 	

  

			
	Acknowledged and Agreed:
	
	M3-BRIGADE ACQUISITION III CORP.
		
	By:	 	
                 

		 	Name: Mohsin Meghji
		 	Title: Executive Chairman of the Board of Directors

  
 9

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