I like to work up playlists for my games - nothing that I'd have to switch during play, but in my Highway to Hell campaign I'll pick out a song to blast as I shout "CREDITS!" at the players, and then put the rest on as background. It's all 70s-80s metal, with some exceptions made for particularly thematic modern songs (Lamb of God's "Walk With Me In Hell" is going to feature in a session dealing with Denarians for sure).
Fitting music to campaigns is, to me, a pretty touchy art. You could just play whatever crap you like at the moment (and sure, I obviously skew my choices towards my own crap), but I find it's better if you can go 1) full-on ambient so nobody recognizes the music but it creates a mood or 2) songs people know but that fit the theme created by the interplay between your setting, the characters, and the adventure they're on.