Name:	ifrs-full_DisclosureOfFinancialLiabilitiesLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The amount of fee and commission expense that the entity does not separately disclose in the same statement or note. [Refer: Fee and commission expense]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2023-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2023-03-23

Name:	ifrs-full_OtherFeeAndCommissionExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of fees paid or payable for professional services.

Name:	ifrs-full_ProfessionalFeesExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of contingent consideration liability expected to be paid.

No definition available.

Name:	mtal_ContingentConsideration
Namespace Prefix:	mtal_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of fees paid or payable for deferred professional services.

No definition available.