v3.26.1
Cover - shares
 6 Months Ended
Jun. 30, 2026
Aug. 12, 2026
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Entity Registrant Name METALS ACQUISITION CORP. II  
Document Period End Date Jun. 30, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0002107724  
Entity File Number 001-43188  
Amendment Flag false  
Entity Incorporation, State or Country Code E9  
Entity Tax Identification Number 00-0000000  
Entity Address, Address Line One c/o Maples Corporate Services Limited  
Entity Address, Address Line Two PO Box 309  
Entity Address, Address Line Three Ugland House  
Entity Address, City or Town Grand Cayman  
Entity Address, Country KY  
Entity Address, Postal Zip Code KY1-1104  
City Area Code +1  
Local Phone Number 345 814 5303  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company true  
Units, each consisting of one Class A ordinary share and one-third of one redeemable warrant    
Document Information [Line Items]    
Title of 12(b) Security Units, each consisting of one Class A ordinary share and one-third of one redeemable warrant  
Trading Symbol MTAL.U  
Security Exchange Name NYSE  
Class A ordinary shares, par value $0.0001 per share    
Document Information [Line Items]    
Title of 12(b) Security Class A ordinary shares, par value $0.0001 per share  
Trading Symbol MTAL  
Security Exchange Name NYSE  
Warrants, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share    
Document Information [Line Items]    
Title of 12(b) Security Warrants, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50 per share  
Trading Symbol MTAL WS  
Security Exchange Name NYSE  
Class A Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   23,000,000
Class B Ordinary Shares    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   7,666,667