I'm a music producer and I have to say for the Metallica example that I completely agree. However... most of the tracks I receive mixed down that I master do indeed end up sounding much better mastered with multiband compression, stereo seperation, very light top end reverb and whatever else is needed.
Yes it makes a difference, yes I bet you have tons of tracks mastered this way in which you have no clue are at -0.2db and still sound great thanks to a good engineer.
Plus metal sucks, the only master I'd apply to that is -inf to the volume.
Heehehehe