I found this blog post on gender and heavy metal culture
very interesting, although I think it is a shame that this researcher apparently wasn't able to interview any women on the subject.
The first thing that struck me was something that a couple of the commenters brought up, which is that this male notion of women at metal shows being "fake", particularly when said women are perceived as physically attractive, is exactly the same thing as the "fake geek girl" phenomenon that we've been seeing in gaming/comics/cosplay circles. Is this a phenomenon in every male-dominated past-time? Or does the fact that geeks/heavy metal fans see themselves as social outcasts or underdogs play a role? (I don't think, for example, that I've ever heard a male football fan complain about "fake" female football fans. But maybe they do this, and I just haven't encountered it.)
The second thing is that this article explained to me a quirk of mine that has always amused me, which is that I spend far more time figuring out what to wear to metal shows than the occasion really warrants. And usually end up rolling my eyes at myself in the mirror and saying, "Seriously, who are you trying to impress?" The answer is that I'm not trying to impress anyone - what I'm doing is trying to ensure that I project enough "authenticity" that I don't get hassled for any of the ways in which I might be different from the rest of the audience - whether it be by being female, fat, younger or older, or just a bit shy and reserved. (The funny thing is, I've never gotten any crap from metalheads for not looking the part. I've caught my share of wardrobe critiques from goths, but that's another matter.)
I have not personally experienced much of the "fake metal girl" attitude in my own attendance at metal shows. When I first started going to metal shows, I was 14 and accompanied by my 12-year-old sister. If we were noticed at all by older male fans, it was as *kids*, to be encouraged and/or protected. All the shows I've been to more recently have had plenty of women in the audience (and probably not coincidentally, at least one woman amongst the performers). The only odd thing I've noticed is that young men sometimes seem a bit baffled when I speak to them - I think this has less to do with my being female as it has to do with their not having a mental frame for a social interaction with someone twice their age who isn't a relative or an authority figure.