<PAGE>   1
                                                                   EXHIBIT 10.28

                               AMENDMENT NO. 1
                                      TO
                               CREDIT AGREEMENT


     THIS AMENDMENT NO. 1 TO CREDIT AGREEMENT ("AMENDMENT") is dated as of June
12, 1998, by and among METAL MANAGEMENT, INC., a Delaware corporation ("MTLM"),
each of the corporations and other entities set forth on ANNEX 1 hereto (MTLM
and each of such corporations and other entities sometimes hereinafter are
referred to individually as a "BORROWER" and collectively as "BORROWERS");
MTLM, acting in its capacity as funds administrator for itself and the other
Borrowers (in such capacity, the "MTLM FUNDS ADMINISTRATOR"); BT COMMERCIAL
CORPORATION, a Delaware corporation (in its individual capacity, hereinafter
referred to as "BTCC"), acting in its capacity as agent (in such capacity,
hereinafter referred to as the "AGENT"), under the "CREDIT AGREEMENT" (as
hereinafter defined); and BTCC in its individual capacity as a "LENDER" (as
defined in the Credit Agreement).  Capitalized terms used herein but not
otherwise defined herein shall have the respective meanings assigned to such
terms in the Credit Agreement.


                                 WITNESSETH:

     WHEREAS, the Borrowers, the MTLM Funds Administrator, the Agent and the
Lender have entered into that certain Credit Agreement dated as of March 31,
1998 (the "CREDIT AGREEMENT"), pursuant to which the Lender has agreed to make
certain loans and other financial accommodations to or for the account of the
Borrowers;

     WHEREAS, the Borrowers, the Agent and the Lender have agreed to amend the
Credit Agreement, on the terms and subject to the conditions hereinafter set
forth;

     NOW, THEREFORE, in consideration of the premises set forth above, the
terms and conditions contained herein, and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
the respective parties hereto hereby agree as follows:

     1.    AMENDMENT TO CREDIT AGREEMENT.  Effective as of the date hereof, upon
satisfaction of the conditions precedent set forth in SECTION 2 below, and in
reliance upon the representations and warranties of the respective Borrowers
and the MTLM Funds Administrator set forth herein, the Credit Agreement is
hereby amended as follows:

           1.1 SECTION 8.2 of the Credit Agreement is hereby deleted in its
entirety and the following language is hereby substituted therefor:

           8.2 CAPITAL EXPENDITURES.



<PAGE>   2


           The Borrowers shall not permit Capital Expenditures for the
      Consolidated Entity in any fiscal year to exceed (A) Consolidated
      Revenues for such fiscal year MULTIPLIED BY (B) two percent (2.00%);
      PROVIDED, that, notwithstanding the foregoing, Borrowers' compliance with
      this SECTION 8.2 shall be determined without giving effect to (I) any
      Capital Expenditure made during the month of April, 1998, with the
      proceeds of Indebtedness evidenced by the Subordinated Notes and (II) any
      Capital Expenditure made after the Closing Date with Equity Offering
      Proceeds constituting Unallocated Equity Proceeds at the time such
      Capital Expenditure was made; PROVIDED, FURTHER, that, concurrently with
      the making of any Capital Expenditure with Unallocated Equity Offering
      Proceeds, the Funds Administrator shall have delivered to the Agent an
      Equity Offering Proceeds Allocation Certificate with respect thereto.

           1.2 SECTION 8.8(A) of the Credit Agreement is hereby amended by 
deleting the reference to the amount of "$2,000,000" appearing in the second    
line thereof and substituting the amount of "$5,000,000" therefor.

           1.3 SECTION 8.8(F) of the Credit Agreement is hereby amended by 
inserting the words "(I) those set forth on Schedule 8.8(i) (to the extent in 
existence on the Closing Date) and (II)"  immediately prior to the word 
"Borrowers" appearing in the first line thereof.

           1.4 SECTION 8.8(G)(VI) of the Credit Agreement is hereby amended by
inserting the words "except as otherwise consented to by the Agent,"
immediately prior to the words "prior to" appearing in the first line thereof.

           1.5 SECTION 8.8(I) of the Credit Agreement is hereby amended by 
deleting the words "SECTION 8.7(I)" appearing in the second line thereof and
substituting the words "SECTION 8.8(I)" therefor.

     2.    CONDITIONS PRECEDENT.  This Amendment shall become effective as of 
the date hereof, upon satisfaction of each of the following conditions:

           (A) Agent shall have received six (6) copies of this Amendment, duly
     executed by Lender, each of the Borrowers and the MTLM Funds Administrator.

     3.    REPRESENTATIONS, WARRANTIES AND COVENANTS.

           3.1 Each of the Borrowers and the MTLM Funds Administrator hereby
represents and warrants to the Agent and each of the Lenders that, after giving
effect to this Amendment:

           (A) All representations and warranties contained in the 


                                     -2-
<PAGE>   3

     Credit Agreement and the other Credit Documents are true and correct in
     all material respects on and as of the date of this Amendment, in each     
     case as if then made, other than representations and warranties that
     expressly relate solely to an earlier date (in which case such
     representations and warranties remain true and accurate on and as of such
     earlier date);

           (B) No Default or Event of Default has occurred which is continuing;

           (C) this Amendment, and the Credit Agreement, as amended hereby,
     constitute legal, valid and binding obligations of the Borrowers and the
     MTLM Funds Administrator, respectively, and are enforceable against each
     of the Borrowers and the MTLM Funds Administrator in accordance with
     their respective terms; and

           (D) the execution and delivery by the Borrowers and the MTLM Funds
     Administrator of this Amendment does not require the consent or approval
     of any Person, except such consents and approvals as have been obtained.

     4. REFERENCE TO AND EFFECT ON THE CREDIT AGREEMENT AND THE OTHER CREDIT
DOCUMENTS.

           4.1 Upon the effectiveness of this Amendment, each reference in the 
Credit Agreement to "this Agreement", "hereunder", "hereof", "herein" or words  
of like import, and each reference in each of the other Credit Documents to the
"Credit Agreement" shall in each case mean and be a reference to the Credit
Agreement as amended hereby.

           4.2 Except as expressly set forth herein, (I) the execution and 
delivery of this Amendment shall in no way affect any of the respective rights, 
powers or remedies of the Agent or any of the Lenders with respect to any Event
of Default nor constitute a waiver of any provision of the Credit Agreement or
any of the other Credit Documents and (II) all of the respective terms and
provisions of the Credit Agreement, the other Credit Documents and all other
documents, instruments, amendments and agreements executed and/or delivered by
any of the Borrowers and/or the MTLM Funds Administrator pursuant thereto or in
connection therewith shall remain in full force and effect and are hereby
ratified and confirmed in all respects.  The execution and delivery of this
Amendment by the Agent and each of the Lenders shall in no way obligate the
Agent or any of the Lenders, at any time hereafter, to consent to any other
amendment or modification of any term or provision of the Credit Agreement or
any of the other Credit Documents, whether of a similar or different nature.

     5.    GOVERNING LAW. THE VALIDITY, INTERPRETATION AND ENFORCEMENT OF THIS
AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE INTERNAL
LAWS AND DECISIONS OF THE STATE OF 



                                     -3-
<PAGE>   4

ILLINOIS, WITHOUT REGARD TO CONFLICT OF LAWS PRINCIPLES.

     6.    HEADINGS.  Section headings in this Amendment are included herein for
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

     7.    COUNTERPARTS.  This Amendment may be executed in any number of
counterparts and by the different parties hereto in separate counterparts, each
of which when so executed and delivered shall be an original, but all of which
shall together constitute one and the same instrument.  Any such counterpart
which may be delivered by facsimile transmission shall be deemed the equivalent
of an originally signed counterpart and shall be fully admissible in any
enforcement proceedings regarding this Agreement.














                            [SIGNATURE PAGE FOLLOWS]


                                     -4-
<PAGE>   5

     IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their proper and duly authorized officers as of
the date first set forth above.

                                    BT COMMERCIAL CORPORATION, in its 
                                    individual capacity as a Lender 
                                    and in its capacity as Agent


                                    By: /s/ Frank Fazio
                                       ----------------------------------
                                    Name:   Frank Fazio
                                         --------------------------------
                                    Title:  Vice President
                                          -------------------------------

                                    METAL MANAGEMENT, INC., a Delaware
                                    corporation, in its individual capacity as
                                    a Borrower and in its capacity as MTLM
                                    Funds Administrator


                                    By: /s/ David A. Carpenter
                                       -----------------------------------
                                    Name:   David A. Carpenter
                                         ---------------------------------
                                    Title: Vice President, General Counsel
                                           and Secretary
                                          --------------------------------




<PAGE>   6

                                    AEROSPACE METALS, INC.
                                    AMERICAN SCRAP PROCESSING, INC.
                                    BRIQUETTING CORPORATION OF AMERICA 
                                    C SHREDDING CORP.
                                    CALIFORNIA METALS RECYCLING, INC. 
                                    CIM TRUCKING, INC.
                                    COMETCO CORP.
                                    COZZI BUILDING CORPORATION
                                    COZZI IRON & METAL, INC.
                                    EMCO TRADING, INC.
                                    FERREX TRADING CORPORATION
                                    FIRMA, INC.
                                    FIRMA PLASTIC CO., INC.
                                    HOUSTON COMPRESSED STEEL CORP.
                                    HOUTEX METALS COMPANY, INC.
                                    THE ISAAC CORPORATION
                                    P. JOSEPH IRON & METAL, INC.
                                    KANKAKEE SCRAP CORPORATION
                                    MAC LEOD METALS CO.
                                    METAL MANAGEMENT ARIZONA, INC.
                                    METAL MANAGEMENT REALTY, INC.
                                    PAULDING RECYCLING,INC.
                                    PROLER SOUTHWEST INC.
                                    PROLER STEELWORKS L.L.C.
                                    SALT RIVER RECYCLING, L.L.C.    
                                    SCRAP PROCESSING, INC.          
                                    SUPERIOR FORGE, INC.            
                                    TROJAN TRADING CO.              
                                    USA SOUTHWESTERN CARRIERS, INC. 
                                    138 SCRAP ACQUISITION CORP.     
                                    R & P HOLDINGS, INC.            
                                    R & P REAL ESTATE, INC.         
                                    CHARLES BLUESTONE COMPANY       


                                    By:  /s/ David A. Carpenter
                                       ----------------------------
                                    Name:    David A. Carpenter
                                         --------------------------
                                    Title:    Vice President
                                          -------------------------

                                    RESERVE IRON & METAL LIMITED PARTNERSHIP

                                    By:  P. JOSEPH IRON & METAL, INC., 
                                         its general partner


                                    By:  /s/ David A. Carpenter
                                       ----------------------------
                                    Name:    David A. Carpenter
                                         --------------------------
                                    Title:   Vice President
                                          ------------------------- 





<PAGE>   7

                                   ANNEX 1
                                      TO
                               AMENDMENT NO. 1
                          DATED AS OF JUNE 12, 1998
                                      
                             ADDITIONAL BORROWERS

1.    AEROSPACE METALS, INC.                    
2.    AMERICAN SCRAP PROCESSING, INC.           
3.    BRIQUETTING CORPORATION OF AMERICA        
4.    C SHREDDING CORP.                         
5.    CALIFORNIA METALS RECYCLING, INC.         
6.    CIM TRUCKING, INC.                        
7.    COMETCO CORP.                             
8.    COZZI BUILDING CORPORATION                
9.    COZZI IRON & METAL, INC.                  
10.   EMCO TRADING, INC.                        
11.   FERREX TRADING CORPORATION                
12.   FIRMA, INC.                               
13.   FIRMA PLASTIC CO., INC.                   
14.   HOUSTON COMPRESSED STEEL CORP.            
15.   HOUTEX METALS COMPANY, INC.               
16.   THE ISAAC CORPORATION                     
17.   P. JOSEPH IRON & METAL, INC.              
18.   KANKAKEE SCRAP CORPORATION                
19.   MAC LEOD METALS CO.                       
20.   METAL MANAGEMENT ARIZONA, INC.            
21.   METAL MANAGEMENT REALTY, INC.             
22.   PAULDING RECYCLING,INC.                   
23.   PROLER SOUTHWEST INC.                     
24.   PROLER STEELWORKS L.L.C.                  
25.   SALT RIVER RECYCLING, L.L.C.              
26.   SCRAP PROCESSING, INC.                    
27.   SUPERIOR FORGE, INC.                      
28.   TROJAN TRADING CO.                        
29.   USA SOUTHWESTERN CARRIERS, INC.           
30.   RESERVE IRON & METAL LIMITED PARTNERSHIP  
31.   138 SCRAP ACQUISITION CORP.               
32.   R & P HOLDINGS, INC.                      
33.   R & P REAL ESTATE, INC.                   
34.   CHARLES BLUESTONE COMPANY