Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 06, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Metacrine, Inc.
Entity Central Index Key	0001634379
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock Shares Outstanding		26,525,627
Security12b Title	Common Stock, par value $0.0001 per share
Trading Symbol	MTCR
Security Exchange Name	NASDAQ
Entity File Number	001-39512
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-2297384
Entity Address, Address Line One	3985 Sorrento Valley Blvd.
Entity Address, Address Line Two	Suite C
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	369-7800
Document Quarterly Report	true
Document Transition Report	false