Not that it has anything to do with me liking metal, but i like chicks with tattoos and piercings and shit like that. I don't think "metalheads" are more likely to be attracted to a certain style in a chick then other people.
Maybe most people are just afraid of not being accepted and being alone so they just talk about things most people can relate to. There's not much risk of rejection when you strike up a conversation about the weather. I've never been outside the country but i highly doubt this behavior is...