While I’m not usually listening to metal, this is still something I know about.
When you buy music, what format it’s in depends on where you bought it.
If you buy from the iTunes Store, you get .m4a files encoded in AAC (most devices and also computers running Windows 7 or newer should handle this)
If you buy from Amazon digitally, you’ll get MP3 files (pretty much everything you touch nowadays should handle this)
If it’s from another source, it depends on what they offer, or if you bought CDs it depends on what format you selected in your media player when copying the CD to your computer.
Listening to music I just do in a media player of choice (I use either Windows Media Player or iTunes on desktop, and the Music app on iPhone)
Managing I usually do in iTunes, since I have an iPhone and have to use that software to put the music on the phone. (if you have an Android phone you can just copy the music onto the phone directly, or use Windows Media Player to do it)
Hopefully this helped you
To be more precise, that’s just my RSS reader (on iOS I use NetNewsWire) with the r/halflife subreddit’s RSS feed added