As I have mentioned before, Satan is a figure commonly associated with heavy metal, but I think Satan’s association with heavy metal is not arbitrary, and not limited to how dark the music is. The presence archetype of Satan in heavy metal music makes a lot of sense to me.
I know that a main reason that Satan or demonic forces got associated with heavy metal is because of a musical interval known as diabolus in musica, or the tri tone, so named because in medieval times it was the sound that was believed to arouse the devil himself. It was believed that the tri-tone was meant to arouse sexual feelings and the forces of darkness, which is why it is associated with the atmosphere of black masses and demonic activity as portrayed in music. It gained importance to heavy metal music because it was that some kind of sound that Black Sabbath evoked in their music, particularly their famous self-titled song, a sound they borrowed from classical music. The band wanted to use that kind of sound because they liked the effect it had for their music. They wanted to create music that was dark, heavy, and doomy, music that reflected the environment they grew up in. Remember, the guys who formed Black Sabbath grew up in a time when the optimism of the 1960’s had dissolved and the 1970’s was coming down on the masses as a time of disillusionment, fear, and woe after the dream of flower power died and became a nightmare. They had no idea they were raising the devil with their music, or were being perceived as such. They had a fascination with the occult, and particularly the dark side, and I suppose they wanted to make music that reflected the darker side of things, but they weren’t intending to raise the devil and they weren’t Satanists. In fact, Geezer Butler, the man who wrote the lyrics, had a pretty orthodox view of things, and his lyrics spoke more against Satan than for Satan. But in the minds of listeners, and for those who would go on to turn their music into the whole of heavy metal, this is the sound that really did evoke Satan itself. Because of this, and other bands that became known for putting Satan on their album covers, writing songs about Satan, or generally employing Satanic imagery, Satan became the archetype for heavy metal music as a whole.
But this still doesn’t answer the question of why this makes sense. All it does is provide background. The reason I feel the archetypal association of Satan with heavy metal music makes sense is because of how heavy metal music as a whole has developed, crystallized, and become what it is today. Satan represented the darker forces that the tri tone evoked, but as the music evolved Satan also came to represent rebellion (though some of that can be attributed to the fact that it shocked the parents of those who listened to it) and the metal mind-set as a whole, simply by becoming attached to the music. Of course in black metal the association is far more involved regarding the tradition of exalting Satan than other forms of music, and a lot of metal bands don’t actively write a lot about the devil, but in a lot of forms of metal flirting with demonic forces is a tradition, if at times a cliche, because of how much Satan has become attached to the music. Satan is an archetype for the music itself, and the mind-set of metal and its fans, and that rings true in a way closely aligned with the philosophy of Satanism perhaps without any conscious intention behind it.
Of course, for a lot of the musicians, it’s all in good fun, and it’s all about finding something that suits the music.