Evil in metal, to me, means realism over morality.
"War is bad," says the hippie.
"War is necessary," says the realist, "Unless you assume that everyone is reasonable."
Natural selection, the triumph of the smarter -- what the hippie hates -- involves war. Natural selection gets reversed when the Crowd appears.
So when bands like Slayer talk about Evil, it's usually in the sense of War Pigs:Now in darkness world stops turning,
ashes where the bodies burning.
No more War Pigs have the power,
Hand of God has struck the hour.
Day of judgement, God is calling,
on their knees the war pigs crawling.
Begging mercies for their sins,
Satan, laughing, spreads his wings.
While humans indulge themselves in a fantasy world of Christ, liberalism, kumbaya, peace, love, etc., reality marches on, and if we ignore that reality, it rules over us. We believe the fantasy on the screen; behind the screen, shadowy deals occur.
Evil in this sense is a metaphor for reality outside of social thinking.
However, in metal it's often overdone. Where Slayer used it in a mythological sense, and early black metal explored the dimensions of postmorality, most of these idiots are just beating the Satan drum because they have no actual ideals:
But I think a guy like ildjarn is really evil, as I said on the other topic, he would probably enjoy killing and torturing people (if he actually hans't done it yet), Bard Eithun killed a guy for nothing, and I read numerous interviews in wich black metal musicians say they admire things that have to do with human suffering, and people who promoted it, lilke Elizabeth Bathory (who has a song dedicated to her by Tormentor, and the band Bathory.)
I never got the fascination with Elizabeth Bathory. I think Venom liked the idea because it was extreme, but the point was that it did not work -- she was a lonely old woman who tried to stave off death (the ultimate Evil) and could not, eventually.
Bart Eithun killed a homosexual. In addition to being homosexual, the guy was useless. Who cares? He wanted the experience of killing. I think it's a good idea for smart people to experience killing of the useless.
Enjoy torturing someone? You should enjoy everything you do, which doesn't mean "pick only what you enjoy" but "find the divinity in everything." If you're going to have to be cruel, you need to live the part.
If you're going to beat the crap out of someone, you need to put your whole spirit into it. The truly evil person will have no emotional response, but will treat it simply like a mechanical task. And if you search your soul, that scares you more than a sadist.
Sadists are interesting because they are addicted to cruelty. An evil person would have none of this. They would torture for a goal, and not be troubled by the method. A sadist is just an alcoholic of pain.