I've always thought some genres should be treated as art, and not others. Like hip-hop - it's entertainment. Same with rock and punk, with maybe a few exceptions. Most metal is no different, except for those raw moments of clarity and greatness that happen once a generation. In the 1970s, it was probably Iron Maiden. In death metal, in the early 1990s, there were a few great bands like Morbid Angel or Amorphis. Black metal hit its stride about the same time, and we got greats like Enslaved, Gorgoroth, Emperor, Burzum, Immortal, Darkthrone, Mayhem, Master's Hammer... that's art. That is metallic art. And all of those bands, in each generation, have some things in common that they sing about and use in their imagery:
1) Morbidity/lack of fear of death
2) Warlike/aggressive
3) No love songs
4) Ambivalent or outright hateful to Christ
5) Ambivalent or outright hateful to Jews
6) Distrust of modern society
7) Love of ancient things

Distrust of herd
9) Like isolation
10) Hedonic
Anyone else notice this? Iron Maiden, Morbid Angel and Immortal are great examples of this.