BQ1: Is AC/DC heavy metal?BQ2: Is Deep Purple heavy metal?BQ3: Is Van Halen heavy metal?BQ4: What is your favourtie heavy metal band?
Hikari's suggestion of DMC is a good one. Beck is also a good call. Personally, I'd go with Nana. If you do go with Beck, make sure you watch the sub instead of the dub, because the songs are much better when sung by native english speakers.
I know of Black Heaven... it's a pretty light anime with romance, it's about the main character re-establishing a metal band. I haven't actually watched it so I'm not sure how much music is in it or exactly what it's like, but it has some kind of metal...
Detroit Metal City aka DMC Don't judge a book by it's cover. The art is meh but the humor is out the roof. I nearly peed my pants 3 times watching that series. Seriously, I had to waddle to the bathroom. It's a gag anime about a guy who wanted to be a soft-pop musician but somehow ended up being the lead singer-guitarist for a death metal band.
if is about a band,then BECK might the best choice..