Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 04, 2019
Document And Entity Information (Abstract)
Entity Registrant Name	Metropolitan Bank Holding Corp.
Entity Central Index Key	0001476034
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		8,319,852
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3