By forgetting the words Death and Black for one moment I'd say Judas Priest, not only because Halford is gay but because of all this optical appearance (Leather).
But as I'm not gay and I don't know anyone who is and listens to Metal, I can only suppose something like Cradle of Filth fits well. I think there must be some kind of gothic-touch, you know, this romantic-depressive feeling, and maybe some sexual intention in either lyrics or presentation.
But after all, every homosexual I know is completely different, since they listen to some kind of happy 80's pop-music, classical music or high-quality female music like Dido or others I can't remember this time. Ballads are also highly recommended...