Related Party Transactions - Additional Information (Details)	1 Months Ended
Mar. 31, 2021 USD ($) $ / shares
Related Party Transaction [Line Items]
Repayment of promissory note - related party	$ 0
Advances from related parties	$ 150,000
Price of warrant \| $ / shares	$ 1.50
Promissory Note with Related Party
Related Party Transaction [Line Items]
Maximum borrowing capacity of related party promissory note	$ 300,000
Related Party Loans
Related Party Transaction [Line Items]
Loan conversion agreement warrant	$ 1,500,000
Related Party Loans \| Working capital loans warrant
Related Party Transaction [Line Items]
Price of warrant \| $ / shares	$ 1.50

Price per share or per unit of warrants or rights outstanding.

No definition available.

Name:	mtal_ClassOfWarrantOrRightPriceOfWarrantsOrRights
Namespace Prefix:	mtal_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of maximum borrowing capacity of related party promissory note.

+ References

No definition available.

+ Details

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

- Definition

The maximum amount which a potential loan could have repaid through issuance of warrants.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow from a long-term borrowing made from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Proceeds from Advances from Affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromRelatedPartyDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for the payment of a long-term borrowing made from a related party where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Payments for Advances from Affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfRelatedPartyDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=mtal_PromissoryNoteWithRelatedPartyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=mtal_RelatedPartyLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=mtal_WorkingCapitalLoansWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: