v3.26.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 27, 2026
Jun. 30, 2025
Document And Entity Information      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2025    
Entity File Number 001-39281    
Entity Registrant Name TMC THE METALS COMPANY INC.    
Entity Incorporation, State or Country Code A1    
Entity Tax Identification Number 00-0000000    
Entity Address, Address Line One 1111 West Hastings Street, 15th Floor    
Entity Address, City or Town Vancouver    
Entity Address, State or Province BC    
Entity Address, Postal Zip Code V6E 2J3    
City Area Code 888    
Local Phone Number 458-3420    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 1,705,461,265
Entity Common Stock, Shares Outstanding   433,188,187  
Documents Incorporated by Reference [Text Block]

Portions of the registrant’s proxy statement in connection with the registrant’s annual meeting of shareholders, scheduled to be held on May 28, 2026, are incorporated by reference in Part III of this report. Except as expressly incorporated by reference, such proxy statement shall not be deemed to be part of this report.

    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001798562    
Amendment Flag false    
Auditor Name Ernst & Young LLP    
Auditor Firm ID 1263    
Auditor Location Vancouver, Canada    
Common Shares, without par value      
Document And Entity Information      
Title of 12(b) Security Common shares, without par value    
Trading Symbol TMC    
Security Exchange Name NASDAQ    
Redeemable warrants, each whole warrant exercisable for one Common Share, each at an exercise price of $11.50 per share      
Document And Entity Information      
Title of 12(b) Security Redeemable warrants, each whole warrant exercisable for one common share, each at an exercise price of $11.50 per share    
Trading Symbol TMCWW    
Security Exchange Name NASDAQ