Metal needs more girls in general, to avoid becoming a sexist genre , like it was in the eighties (just watch a Manowar gig for proof).
If someone is a talented drummer/guitarist/bass player/singer etc. then it shouldn't matter what genitals they happen to have been born with.
Metallica have both the best and worst albums out of all of them (Master of Puppets and St. Anger), in my opinion. Other than that, all of the Big Four are way too inconsistent, apart from Slayer, whose songs all sound the same anyway.