Whereas you listen to metal, I try to listen to something peaceful to help me relax. I don't like playing a frantic soccer game, so I tend to warm up in a very laid back manner.
Mostly stretching for a good bit, pass the ball around with my mid-field buddies, and then play some 5v5 keep away in a big coned off area. Oh, and I always lace my boots up the exact same way.