I have heard enough music in my life to make a qualified opinion.
I don't listen to Metal, as my hearing is damaged and I can't listen to hard core as it grates my ears..
Def Lepard, hardly heavy, but they had very good dynamics, which made Hysteria easy to listen to ( this was as far as I got with metal, not my cupp of tea, pint of beer, flagan of wine).
I have found when listening to some metal, it does not have dynamics, hence why I said its a waste to those Dynaudio speakers..
Death metal is even more of a waste, and I have heard plenty, 2 of my mates listen to all sorts of it...
When comparing Metal to other genres, I find it sounds flatter, hence once again, Dybs are wasted, but as some people have pointed out, there is this CD and that CD..
Get some classical, put your best Meta CD on, and your average Classic CD on, and I bet you the Classical wins..
Not rocket science, just the way the dynamics are produced..