outta curiousity, what kinda sound reference(bands, recording etc) would fall into "metal sounding" territory for you.
One interesting to note is that most of the time, we tend to associate sound differently and according to the music that we are exposed to or have experience with. Thus, in some context, the geetar sound from judas priest might be metal for those who prolly know its history/heaviest music for them whereas some would proly hear metal sounding as only the sound of highly distorted/harsh geetar tone with little mids.
Other then amount of gain, there should be other factors at play as well, aka the voicing of the amp, the eq setting and whether the "metal sound" which you might be familiar with, is it from recording, cd(both with post production done on it) or live sound with their sound engineer tweaking it suitable for live setting etc.