v3.25.2
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2025
Jul. 31, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Trading Symbol MTUS  
Title of 12(b) Security Common shares  
Security Exchange Name NYSE  
Entity Registrant Name METALLUS INC.  
Entity Central Index Key 0001598428  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   41,826,462
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Document Quarterly Report true  
Document Transition Report false  
Entity Incorporation, State or Country Code OH  
Entity Address, Address Line One 1835 Dueber Avenue SW  
Entity Address, City or Town Canton  
Entity Address, State or Province OH  
City Area Code 330  
Local Phone Number 471.7000  
Entity Address, Postal Zip Code 44706  
Entity Tax Identification Number 46-4024951  
Entity File Number 1-36313