They are neither satanic nor using shock value, You obviously are ignorant. The symbols are beautiful and meaningful. If you study satanic writings, are you suddenly a satanist? If you talk about the things you studied, does that make you satanist? No, it doesn't. If you make art, and someone says it looks satanic, it doesn't mean that you are.
I also assume you don't listen to metal, and furthermore don't have any conceptual understanding of how metal works. Metal is an emotional journey, unlike slow and crappy rock. You can change the emotions you feel based on sight and sound. "Shock value" doesn't apply here. The lyrics and graphics are meant to stimulate and arouse, not to shock. The imagery guides you, when your done riding the imagery and the tunes, you can be as devout to whatever religion you want to be.