Curious topic.
There are some extreme metal bands I like sonically-- Sunn 0))), Celtic Frost's To Mega Therion is a great bombastic everything but the kitchen sink Monty Python mad genius album (I mean, how many metal bands came with its own timpani, horn section and opera singers?), Electric Wizard, Earth. I'm centric to experimental sounds and generally don't listen to the words. I'm sure Electric Wizard would say their satanic lyrics are just a schick, and I have no doubt a lot of their lyrics are stupid. Most of Sunn 0)))'s music is instrumental-- it's an avant garde sounds band. A friend of mine said she didn't think Sunn 0))) counted as music.
I don't like death metal, 80% because I can't stand distorted vocals. Hate electronically distorted vocals in top 40 hip hop music and in death metal and in the Chipmunks' Christmas Carols. A Rolling Stone critic once famously called a metal band's sounding like 'the cookie monster throwing up.' I couldn't have worded it better. So, no, I don't give a thumbs up to Norwegian Black Metal from what I've heard. I find it hard to take seriously any Satanism in music and think most of the time it's a stage act. I take it no more seriously than the Vampiricism in the Twilight Series and Vampire Diaries. If a band is being serious about it, I wouldn't call it evil but stupid.
Actually, a lot of old blues songs are about the singer's relationship and struggles with the Devil. Robert Johnson is the quintessential example. The story of Johnson having sold his soul for his guitar playing skills is a part of his legend, and his lyrics are dark and haunting.
Youtube: Robert Johnson "Me and the Devil Blues" (1937)