Well when I first meet someone, I usually say I like Rock. Then see if he likes rock too. If he doesn't, I quit the music conversation there. But if he does, I kinda tells him that I like hard rock, to the extent of metal. So then we talk. But most of the time, the guy doesn't know at least 80% of the bands I listen to. The ones he knows are Pink Floyd and Dream Theater, but that's usually about it.
One time I ran into this guy who liked Nirvana and stuff. I asked him if he listens to metal and he said no. Then I asked again, "what do you think about metal?" Then his answer was something like, "It's a pretentious genre." Although I want to disagree to the fullest, I really had to agree that at least 80% of metal bands out there are really pretentious with almost no music.
Edit: And yes, he liked Nirvana, so his opinion doesn't really count.