It's really interesting if you examine a lot of the recurring themes throughout many eras of popular music. It's quite obvious that such themes aren't nearly as prevalent in the current popular music plane, but if you most at most Scandinavian metal music you'll be able to identify with what they're saying. Of course, you can't forget things like Black Label Society and Resistance Records, though I haven't heard much from them overall.
It's not easy to overshadow the greats like Slayer, Megadeth, and Metallica (it's pretty clear what their messages were), but if you really investigate a lot of 80s, and even 70s heavy metal it also becomes quite clear what they were talking about, and who they so hated, and in most cases, hatred is a good thing when used to inspire creativity.
Some of my favorite bands are (aside from the three previously mentioned) are Bathory, Judas Priest, Darkthrone, Emperor, Behemoth, Morbid Angel, Bal-Sagoth, Hammerfall, Burzum, Obsidian Gate, Amon Amarth, and Mercyful Fate.
The good thing is that a lot of these bands are rife with pagan symbolism and epic soundscapes with a lot of guitar solos and blast-beats, and everybody loves those :)
