Will a MetroPCS SIM card work in an iPhone 12 Mini locked to T-Mobile?

I currently have an older iPhone with a MetroPCS account and associated SIM card. Now seeking to upgrade to a iPhone 12 Mini. Have opportunity to buy one that's locked to "T-Mobile." Will my MetroPCS SIM card work in the T-Mobile phone as is -- or would I need to get the phone unlocked?

The reason I ask is that now MetroPCS is just a corporate subsidiary of T-Mobile, so basically they're the same company. But I don't know if their SIM cards are interchangeable in the same iPhone.