Pray about it, and see how you feel afterwards!
I'm a big death metal fan, and a Christian at the same time, and that isn't easy. Most of the lyrics are offensive, yet I focus solely on the music (and you can't really understand the vocals anyway). The best advice I can give you is the above sentence. If you really feel that you shouldn't be listening to it, then don't.
I heard that the singer actually died of a popped blood vessel in his brain from over-screaming at the concert.