Metal is violence and that has nothing to do with lyrical themes or the behavior of its fans. Metal is a sonic attack against consciousness, an aggressive blow dealt to rational analysis in an attempt to break it down to base instinct wherein one doesn't think about the sounds so much as experience them directly as primal emotion.
Headbanging isn't a dance. It's an autonomous reaction, a survival mechanism to channel the savage raw energy a listener is being bombarded with. People who think all metal is the same are wrong. Like getting punched in the nose, the brass-tacks bottom-line practical effect is the same. But there's a huge difference in delivery between the cold efficiency of a boxer's jab, the grace of capoeira and the sloppy savagery of a drunken haymaker. And that's what makes it exciting.
Boise shredders Krystos are most comparable to fine kung fu: both badass and graceful to see in action. Their falsetto high notes, super-fast synchronized guitar lines and tight arrangements are delivered as effortlessly as Jet Li dancing across rooftops in Crouching Tiger Hidden Dragon like it were second nature: Tao te progressive thrash. Catch them with Fault Paradox, Ripchain and The Reptilians.