When I was young I liked metal music a lot. I listened Iron Maiden, Metallica and dozen other bands. As I grew older my interest in that music declined until completely faded out.
Recently I listened to some metal songs I used to like in my teens and suddenly I realized that my distaste to this music is rooted not in the "style" of the music itself but probably because of the heavily exploited theme of evil (violence, chaos, destruction...) in most of the songs. There are, of course, some bands and some songs that do not use the theme of evil but as far as I can see this exception only proves the rule. Just look at the names of popular bands - Judas Priest, Black Sabbath, Slayer, Megadeth, Anthrax...
So here is the question - is there any kind of research on why evil themes are so attractive to the creators of such kind of music? Is it happening because of something inherent to this genre, something that's naturally evoked by the signature or structural features of that's musical genre? And I can see that theme of bravery, heroism or great achievements might fit to this genre but this is not what's usually happening.
Oh, and it doesn't have to be a research, any good thought or article on this matter is fine too.
This is a pure curiosity question, I am sorry for grammar errors (English is not my native) and possibly looking naive or making unjustified generalizations - by no means I am an expert in music.