AEJim:
I think there are a few conflicts between Heavy Metal music and the traditional Hi-Fi values which always leads to some elitist snobbery from those who listen to "tinkly piano jazz". It's usually down to the recording quality/production, which in many cases is a completely unjustified criticism.
It's been a few years since I've been into "real" heavy metal so I'm not too familiar with the newer material but I can tell you that, for example, Pantera have some brilliantly made albums which really do sound amazing on a good system. We use AC/DC, Sabbath, Rage Against the Machine and Nirvana as part of our program of test material when developing new speakers. Saying that - there is some awfully recorded stuff around, in particular a large portion of 80's albums are highly compressed and not worth a listen (the same can be said of any genre though!).
It's very easy to produce a good sound when you only have one cleanly recorded instrument playing, hence that kind of material being the most prevolent in Hi-Fi show demonstrations - it's far harder to make a group of overdriven guitars, pounding drums and gravelly shouting sound "pleasant". In my opinion this is actually a far sterner test of your system - the old Hi-Fi benchmarks of soundstaging, separation, depth, timing and tonal quality are actually still evident on many of these recordings! You don't always get the huge dynamic swings of Classical music but some of the bass guitar/drum solo's are equally revealing of a system's capabilities.
The other consideration when listening to Heavy Metal/Rock is volume of course! This kind of music just doesn't sound right when it's quiet, many perfectly good systems just aren't so good at higher levels and the sound can harden up noticeably. You're probably best off aiming for as much power as possible in an amp, speakers with larger/multiple drivers and a source component which isn't too harsh and thin with good midrange attack for those snares and guitar solo's. This is generalisation at it's best of course since there are always exceptions to the rule.
One of the best post i ever read on this forum
IMO, metal system is hardest to build and certainly the most expensive! Too many people turn their nose at the metal recording but get the synergy right and nothing else matter!