Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Document And Entity Information (Abstract)
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity Registrant Name	METROPOLITAN BANK HOLDING CORP.
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		8,294,801
Entity Central Index Key	0001476034
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false