I don't get much into the "growling" type or the "death-metal" lyrics. I like "clean" sounding metal, the more melodic stuff. More into the mainstream metal and hard rock-anything from Maiden to Poison and in-between. I do like Slayer, though. If you listen to their lyrics they're actually a quite conservative band. "Silent Scream" is a song that is against abortion.
I'm actually amazed by some of the poignancy of some of the love ballads. They don't always sound great (to me) right off the bat, but at least the lyrics are pretty nice, sometimes. Not like rap where we are only "bitches" and only good for "doing", then slap her around.