I know people might disagree, but I gotta get it off my chest.... it's shallow to try at a romantic relationship based on similar taste in music. I'm glad my partner and I have similar tastes, don't get me wrong, and having a date for shows is a REALLY nice bonus, but I wouldn't consider it a huge selling point. Plenty of women/men who like non-mainstream metal suck, it's not any indication whatsoever of a good personality. Although I guess it's a nice start.
A better route is to find someone who's interested in the same kind of lifestyle as you, and chances are, they'll like you enough to be open to your music. Like if your OKC profile is less than a paragraph long, don't go hittin up a chick who's written an entire fucking essay, even if it's about how much she loves metal. You're different people. And if you like gaming with a bag of fritos, don't go hittin up a gym rat.