Even I've mostly felt that the Axioms are too bright for metal. However, if I have to make a choice of excellent recordings, I would go with these:
Bon Jovi: Keep the Faith
Metallica: Ride the Lightning, Master of Puppets, Kill 'em All
Judas Priest: Metal Works (This recording is lovely)
Rammstein: Mutter, Sehnsucht, Herzeleid (Asche zu Asche is fantastic in this album)
Cinderella: Night Songs
Metallica: S&M (Really punishes the speakers with so many instruments)
Most of AC/DC's recordings have too much boom in the upper bass area. Megadeth's recordings were hollow on some albums though I don't remember which ones. Iron Maiden was too noisy.
I'm not aware of the new bands. Perhaps Linkin Park is worth a mention as their songs sounded like they had good recordings.
In fact, even today, I restrict myself from listening to rock music on the axioms and prefer to hear them through my Sennheiser headphones. All other forms of non-rock music seem to sound better on the Axioms. I haven't been able to pinpoint why but it just is.
