The music genre is not the best place to start when choosing a system. Speakers are by far the most critical decision, so start there. So how do you decide which speakers? Your room, distances to the listening position, desired dynamic range, linearity, power response are a few of the main considerations. Then you'll end up choosing speakers as adept at metal as they are with Bach concertos.
So, what's the room like? What sort of system? (Stereo, 2.1, multichannel?) Capable of big dynamics/high spl? How much so? Be specific, at least as much as possible.
Speaker choice will dictate amp requirements, and the rest will fall into place depending on your needs/desires for features.