You are very much in the minority. I grew up with metal. All my friends were into metal. I was in metal bands. Been there, done that, many times over. I know metal, I know metal fans, and I know the metal mindset. Most of the metal heads I knew were ONLY into metal, and that's it.
Get the video "heavy metal parking lot" and watch it very carefully to fully understand the metal crowd. They were not an open minded bunch of free thinkers. In fact, they all seemed very much alike, to the bands they liked, style of clothing, favorite brand of car or even beer....
Point is, I grew up during the metal years, the heyday of metal. And not one of my friends growing up could dig something like Frank Sinatra, ANY type of jazz or any type of music other then metal.
Oh, of course there are exceptions, and you are probably one of them....but you are not speaking for the majority of them, believe me.
I understand metal. It was basically my first favorite music...well, at least add hard rock in general in there...point is, I outgrew it a long time ago...but I was there when the sound transitioned from english heavy metal bands to the american bands like metallica and megadeth, who are basically the template for most if not all modern metal.