<PAGE>

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                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                          ---------------------------

                                  FORM 10-K/A
                               (AMENDMENT NO. 1)

<Table>
<S>      <C>
[X]      ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
         FOR THE FISCAL YEAR ENDED MARCH 31, 2006

[ ]      TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
         FOR THE TRANSITION PERIOD FROM  __________________________ TO  _________________________
</Table>


                COMMISSION FILE NUMBER 0-14836
           ---------------------------------------------------------
                             METAL MANAGEMENT, INC.
             (Exact Name of Registrant as Specified in Its Charter)
           ---------------------------------------------------------

<Table>
<S>                                            <C>
                   DELAWARE                                      94-2835068
(State or Other Jurisdiction of Incorporation       (I.R.S. Employer Identification No.)
               or Organization)
325 N. LASALLE STREET, SUITE 550, CHICAGO, IL                      60610
   (Address of Principal Executive Offices)                      (Zip Code)
</Table>

       Registrant's telephone number, including area code: (312) 645-0700

          SECURITIES REGISTERED PURSUANT TO SECTION 12(B) OF THE ACT:

                             None
          SECURITIES REGISTERED PURSUANT TO SECTION 12(G) OF THE ACT:
                          Common Stock, $.01 par value

      Series A Warrants (Expiration Date June 29, 2006)
                          ---------------------------

     Indicate by check mark if the Registrant is a well-known seasoned issuer,
as defined in Rule 405 of the Securities Act. Yes X      No _

     Indicate by check mark if the Registrant is not required to file reports
pursuant to Section 13 or Section 15(d) of the Act. Yes  _       No X

     Indicate by check mark whether the Registrant: (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
Registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes X      No  _

     Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of Registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [     ]

     Indicate by check mark whether the Registrant is a large accelerated filer,
an accelerated filer, or a non-accelerated filer. See definition of "accelerated
filer and large accelerated filer" in Rule 12b-2 of the Exchange Act.
     Large accelerated filer  _      Accelerated filer X      Non-accelerated
filer  _

     Indicate by check mark if the Registrant is a shell company (as defined in
Rule 12b-2 of the Exchange Act). Yes  _      No X

     The aggregate market value of common stock held by non-affiliates of the
Registrant was approximately $622 million as of September 30, 2005, the last
business day of the Registrant's most recently completed second fiscal quarter,
based on a closing stock price of $25.35 per share.

     Indicate by check mark whether the Registrant has filed all documents and
reports required to be filed by Section 12, 13 or 15(d) of the Securities
Exchange Act of 1934 subsequent to the distribution of securities under a plan
confirmed by a court. Yes X      No  _

     As of May 10, 2006 the Registrant had 26,053,933 shares of common stock
outstanding.

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<PAGE>

                                EXPLANATORY NOTE

     In connection with the filing of this Form 10-K/A and pursuant to Rules
12b-15, 13a-14(a) and 13a-14(b) under the Securities Exchange Act of 1934, as
amended, the Registrant is including currently dated certifications. This Form
10-K/A does not reflect events occurring after the filing of the Registrant's
Form 10-K on May 25, 2006 or modify or update the disclosure contained therein
in any way other than as required to reflect the inclusion of the Metal
Management, Inc. Employee Stock Purchase Plan financial statements and report of
the independent registered public accounting firm thereon.

                                    PART IV

ITEM 15.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

     (a) The following documents are filed as a part of this report:

          (1) Financial Statements:

<Table>
<Caption>
                                                              PAGE
                                                              ----
<S>                                                           <C>
Report of Independent Registered Public Accounting Firm       F-1

Statement of Financial Condition as of March 31, 2006         F-2

Statement of Income and Changes in Plan Equity from Plan
  Inception through March 31, 2006                            F-3

Notes to Financial Statements                                 F-4
</Table>

          (3) Exhibits:

NUMBER AND DESCRIPTION OF EXHIBIT

<Table>
<S>            <C>
         23.1  Consent of PricewaterhouseCoopers LLP




         31.1  Certification of Daniel W. Dienst pursuant to Section
               240.13a-14 of the Securities Exchange Act of 1934, as
               amended, as adopted pursuant to Section 302 of the
               Sarbanes-Oxley Act of 2002.




         31.2  Certification of Robert C. Larry pursuant to Section
               240.13a-14 of the Securities Exchange Act of 1934, as
               amended, as adopted pursuant to Section 302 of the
               Sarbanes-Oxley Act of 2002.




         32.1  Certification of Daniel W. Dienst & Robert C. Larry pursuant
               to 18 U.S.C. Section 1350, as adopted pursuant to Section
               906 of the Sarbanes-Oxley Act of 2002.
</Table>
<PAGE>

                                   SIGNATURES

     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, registrant has duly caused this report to be signed on its
behalf by the undersigned, hereunto duly authorized on July 31, 2006.

                                          METAL MANAGEMENT, INC.

                                          By:      /s/ Robert C. Larry
                                            ------------------------------------
                                            Robert C. Larry
                                            Executive Vice President, Finance,
                                              Chief Financial Officer, Treasurer
                                              and Secretary
                                            (Principal Financial Officer)
<PAGE>

            REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To: The Compensation Committee of the Board of Directors of Metal Management,
Inc. and the
Participants of the Metal Management, Inc. Employee Stock Purchase Plan

     In our opinion, the accompanying statement of financial condition and the
related statement of income and changes in plan equity present fairly, in all
material respects, the financial condition of the Metal Management, Inc.
Employee Stock Purchase Plan (the "Plan") at March 31, 2006, and the income and
changes in plan equity for the period from inception to March 31, 2006 in
conformity with accounting principles generally accepted in the United States of
America. These financial statements are the responsibility of the Plan's
management. Our responsibility is to express an opinion on these financial
statements based on our audit. We conducted our audit of these statements in
accordance with the standards of the Public Company Accounting Oversight Board
(United States). Those standards require that we plan and perform the audit to
obtain reasonable assurance about whether the financial statements are free of
material misstatement. An audit includes examining, on a test basis, evidence
supporting the amounts and disclosures in the financial statements, assessing
the accounting principles used and significant estimates made by management, and
evaluating the overall financial statement presentation. We believe that our
audit provides a reasonable basis for our opinion.

PricewaterhouseCoopers LLP

Chicago, IL
July 31, 2006

                                       F-1
<PAGE>

                             METAL MANAGEMENT, INC.
                          EMPLOYEE STOCK PURCHASE PLAN

                        STATEMENT OF FINANCIAL CONDITION

<Table>
<Caption>
                                                              MARCH 31, 2006
                                                              --------------
<S>                                                           <C>
ASSETS
  Receivable from Metal Management, Inc.
     (Notes 1 and 2)                                             $90,037
                                                                 -------
                        TOTAL ASSETS                             $90,037
                                                                 =======


LIABILITIES AND EQUITY
  Obligations to purchase Metal Management, Inc.
     common stock (Notes 1 and 2)                                $90,037
  Plan equity                                                          0
                                                                 -------
                TOTAL LIABILITIES AND EQUITY                     $90,037
                                                                 =======
</Table>

               See accompanying notes to the financial statements

                                       F-2
<PAGE>

                             METAL MANAGEMENT, INC.
                          EMPLOYEE STOCK PURCHASE PLAN

                 STATEMENT OF INCOME AND CHANGES IN PLAN EQUITY

<Table>
<Caption>
                                                                  PERIOD OF
                                                              INCEPTION THROUGH
                                                               MARCH 31, 2006
                                                              -----------------
<S>                                                           <C>
Plan equity at inception                                          $       0
Participant contributions                                           172,265
Benefit payments (Note 1 and 2)                                    (172,241)
Amounts refunded to Plan participants                                   (24)
                                                                  ---------
Plan equity at the end of the year                                $       0
                                                                  =========
</Table>

               See accompanying notes to the financial statements

                                       F-3
<PAGE>

                             METAL MANAGEMENT, INC.
                          EMPLOYEE STOCK PURCHASE PLAN
                         NOTES TO FINANCIAL STATEMENTS

NOTE 1 -- DESCRIPTION OF THE PLAN

     In July 2005, the Board of Directors of Metal Management, Inc. (the
"Company") adopted the Metal Management, Inc. Employee Stock Purchase Plan (the
"Plan"). The Plan was approved by the Company's stockholders in September 2005
and became effective on October 1, 2005. The Compensation Committee of the Board
of Directors administers the Plan. The Company has reserved a total of 1,000,000
shares of common stock for issuance under the Plan.

     The Plan permits eligible employees to make regular, systematic purchases
of the Company's common stock directly from the Company through payroll
deductions. Substantially all employees of the Company are eligible to
participate except for:

     - an employee who customarily is employed (within the meaning of Section
       423(b)(4)(B) of the Internal Revenue Code of 1986 ("Code")) 20 hours or
       less per week by the Company,

     - an employee who has not been continuously employed (within the meaning of
       Code Section 423(b)(4)(A)) by the Company for at least 90 days,

     - an employee who would own (immediately after the grant of an option under
       this Plan) stock possessing 5% or more of the total combined voting power
       or value of all classes of stock of the Company based on the rules set
       forth in Section 423(b)(3) and Section 424 of the Code, and

     - any highly compensated employee (within the meaning of Code Section
       414(q)) whose annual compensation rate is at least $170,000, or other
       group of highly compensated employees as designated by the Compensation
       Committee.

     Voluntary employee contributions are deducted from participants' base pay
each pay period and are held for the participants' accounts. All funds held by
the Company under the Plan are included in the general assets of the Company.

     On the first day of each of the four purchase periods (April 1, July 1,
October 1 and January 1), participants in the Plan are granted an option to
purchase shares of the Company's common stock. Within two days after the last
day of each purchase period (June 30, September 30, December 31 and March 31),
the Company uses participant contributions, net of refunds, to purchase shares
of the Company's common stock for each participant. Contributions that exceed
the Plan provisions or Code limits are refunded to participants. The purchase
price per share to the participant is equal to 85% of the lesser of the market
value, as defined, of the Company's common stock on the first or last day of the
purchase period.

     For the purchase period ending December 31, 2005, a total of 4,158 shares
of the Company's common stock were purchased. All shares are registered in the
participant's name in book entry form with the Plan's custodian.

     Participants may terminate contributions and withdraw from the Plan at any
time up to ten days prior to the exercise date in any purchase period. Even
though there are no current intentions to do so, the Board of Directors may
terminate the Plan at any time. Stock purchase transactions in process at the
time of such termination cannot be modified or canceled without the written
consent of the participants.

                                       F-4
<PAGE>

                             METAL MANAGEMENT, INC.
                          EMPLOYEE STOCK PURCHASE PLAN
                         NOTES TO FINANCIAL STATEMENTS

NOTE 2 -- SIGNIFICANT ACCOUNTING POLICIES

Basis of Accounting
The accompanying financial statements have been prepared on the accrual basis of
accounting.

Use of Estimates
The preparation of financial statements in conformity with U.S. generally
accepted accounting principles requires Plan management to make estimates that
affect the reported amounts of Plan assets and liabilities and to disclose any
contingent assets and liabilities at the date of the financial statements and
the reported amounts of changes in Plan equity during the reporting period.
Actual results could differ from those estimates, and the differences could be
material.

Benefit Payments
Benefit payments represent the purchases of common stock or common stock to be
purchased (see Note 4 -- Subsequent Events).

Risks and Uncertainties
The Plan does not hold assets of the individual Plan participants but rather
holds as its only asset the accumulated contributions representing payroll
deductions due from the Company. As such, the Plan is exposed to concentration
of credit risk. The Plan also provides for investment in shares of common stock.
Shares of common stock are exposed to equity price risk. Due to the level of
risk associated with shares of common stock and the level of uncertainty related
to changes in the value of shares of common stock, it is at least reasonably
possible that changes in the risks in the near term would materially affect the
value of the securities acquired by the participants and will affect the number
of shares of common stock that a participant can acquire from his or her
accumulated contributions prior to acquisition of the common stock.

Plan Administration
The Plan is administered by the Compensation Committee of the Company's Board of
Directors, which consists of four outside directors.

Plan Expenses
The Company pays for the Plan's administrative expenses.

NOTE 3 -- FEDERAL INCOME TAXES

The Plan qualifies as an Employee Stock Purchase Plan under Section 423 of the
Code. Issuances of shares under this Plan are not intended to result in taxable
income to participants in the Plan based on provisions in Section 423 of the
Code.

NOTE 4 -- SUBSEQUENT EVENTS

For the Offering Period ended March 31, 2006, Plan participants' accumulated
payroll deductions amounted to $90,037 and have been recorded as a contribution
receivable by the Plan as of March 31, 2006. Subsequent to March 31, 2006, the
aggregate of these accumulated deductions were used to purchase 4,452 whole
shares of common stock, which were issued by the Company to the Plan custodian
subsequent to March 31, 2006. The shares of common stock purchased subsequent to
March 31, 2006 had a closing market value of $140,906 as of the exercise date.

                                       F-5