EX-32.1

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Exhibit 32.1

CERTIFICATION

Pursuant to 18 U.S.C. Section 1350,

As Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

In connection with the Annual Report of Metallus Inc. (the “Company”) on Form 10-K for the period ended December 31, 2025, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), each of the undersigned officers of the Company certifies, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to such officer’s knowledge:

(1)

The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)

The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of the dates and for the periods expressed in the Report.


Date:	February 20, 2026	/s/ Michael S. Williams
		Michael S. Williams Chief Executive Officer (Principal Executive Officer)
Date:	February 20, 2026	/s/ John M. Zaranec
		John M. Zaranec Executive Vice President and Chief Financial Officer (Principal Financial Officer)