How does Apple Music subscription affect the music I own?

I've found a lot of questions about similar things, but none that will actually answer my specific question, so hopefully someone can help me out here—I just got a new MacBook Pro after having a mid-2013 one for many years, and my old iTunes files are all in folders of .m4a files. (I airdropped the original files manually, for reference—didn't use any of the migration features.)

Clicking the files opens/plays them in Apple Music. It would certainly be convenient to open them all in Apple Music, sort them into their respective albums, etc. so I can listen to them like I used to listen to iTunes.

However, I'm well aware by this point that my usage of Apple Music is a three-month free trial. My specific question is what does that mean? What will I lose access to? The ability to sort the files into albums and listen conveniently? The ability to open .m4a files at all, unless I download VLC Media Player or something? Is Apple Music somehow going to lock access to the files I owned before I ever tried to use it? Or do I still get to use the app for my own stuff, just without access to the online streaming service? I'd appreciate it if someone could clear this up.