EXHIBIT 5.1
 
September 2, 1998
 
ISG Resources, Inc.
(formerly JTM Industries, Inc.)
136 East South Temple, Suite 1300
Salt Lake City, Utah 84111
 
Ladies and Gentlemen:
 
We have acted as special counsel to ISG Resources, Inc. (formerly, JTM
Industries, Inc.), a Texas corporation (the "Company"), in connection with the
Company's offer to exchange (the "Exchange Offer") its 10% Senior Subordinated
Notes due 2008 (the "Exchange Notes"), which have been registered under the
United States Securities Act of 1933, as amended, for its 10% Senior
Subordinated Notes due 2008 (the "Restricted Notes"). The $100,000,000 aggregate
principal amount of the Company's Restricted Notes were issued and sold by the
Company, pursuant to the Purchase Agreement (the "Purchase Agreement"), dated
April 17, 1998, among the Company, certain subsidiaries of the Company, and
NationsBanc Montgomery Securities LLC and CIBC Oppenheimer Corp. (collectively,
the "Initial Purchasers") and issued pursuant to an Indenture (the "Indenture"),
dated April 22, 1998, among the Company, the Subsidiary Guarantors (as defined
below) and U.S. Bank National Association, as trustee (the "Trustee"). The
Restricted Notes are guaranteed (the "Subsidiary Guarantees"), jointly and
severally, on a senior subordinated basis by all existing domestic subsidiaries
of the Company (the "Subsidiary Guarantors").
 
    For the purposes of this opinion, we have examined the preliminary
registration statement filed with the Securities and Exchange Commission on June
5, 1998, the Indenture, relevant documents of the Company and each Subsidiary
Guarantor and such other documents and certificates as we have deemed necessary
for the purposes of the opinion expressed below. In such examination we have
assumed the genuineness of all signatures and the authenticity of all documents
including photocopies and facsimile copies of documents submitted to us as
originals and the conformity with the original of all documents submitted to us
as copies. Capitalized terms used but not defined herein shall have the meanings
ascribed to them in the prospectus pursuant to which the Exchange Notes are
being offered.
 
    Based upon the foregoing, we are of the opinion that, assuming due
authorization, execution and delivery of the Exchange Notes and the Subsidiary
Guarantees by the parties thereto and due authentication of the Exchange Notes
by the Trustee, and upon acceptance of the Restricted Notes in exchange for the
Exchange Notes, the Exchange Notes and the Subsidiary Guarantees will constitute
legally binding obligations of the Company and each of the Subsidiary
Guarantors, respectively, entitled to the benefits of the Indenture and
enforceable against the Company and each of the Subsidiary Guarantors,
respectively, in accordance with their terms, except as (A) such enforceability
may be limited by bankruptcy, insolvency, fraudulent transfer, fraudulent
conveyance, reorganization, arrangement, moratorium or similar laws relating to
or affecting the enforcement of creditors' rights generally and may be subject
to general principles of equity (regardless of whether such enforceability is
considered in a proceeding in equity or at law), and (B) the availability of
equitable remedies may be limited by equitable principles of general
applicability.
 
    We render the foregoing opinion as members of the Bar of the State of New
York and express no opinion as to laws other than the laws of the State of New
York.
 
    Our opinion is given as of the date hereof and we assume no obligation to
update or supplement this opinion to reflect any facts or circumstances which
may hereafter come to our attention or changes in law which may hereafter occur.

    This opinion is solely for the benefit of the addressees named above and may
not be used, circulated, quoted or otherwise referred to for any purpose without
our prior written consent.
 
    We consent to the reference to our firm under the heading "Legal Matters" in
the prospectus forming part of the Form S-4 Registration Statement and we
consent to the filing of this opinion as an exhibit to such Registration
Statement. In giving this consent, we do not thereby admit that we are within
the category of persons whose consent is required to be filed with the
Registration Statement under the provisions of the United States Securities Act
of 1933, as amended, or the rules and regulations promulgated thereunder.
 
                                        Very truly yours,
 
                                        Morgan, Lewis & Bockius LLP
 
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