I like heavy metal very much, but it's not currently popular in Japan.
In the end of 1980s, it was popular in Japan. Therefore there were a lot of metal bands, but boom didn't last long. In the early 1990s, there were few bands remained.
The most renowned metal band is "Loudness" who performed in early 1980s and they are still performing their music. In addition, some young bands are growing up. one of them is "galneryus" and they are my most favorite band.
If you like, please listen to their music!