The expression "They're all metalheads"

Marty Friedman is a rock guy. The 51-year-old spent much of the 1990s as the lead guitarist in thrash metal pioneers Megadeth, eventually taking the odd-seeming move of decamping from the United States to Japan and settling into a new role as a cheerleader for J-pop. Through his experiences in the Japanese music industry, however, one thing that struck him was just how natural a move that really was.

“Coming from a metal background, what I’ve always noticed is that working in the music business, they’re all metalheads,” Friedman tells The Japan Times. “But there’s no money in metal, so they try so hard to mix it with other things . . . I’ve done so many things where it’s a pop project but (people will say), ‘Make this metal. Play your ass off on this!’ and I love doing it because I love to inject my own thing into everything.”

In the above passage, what does this "they're all metalheads" mean? Does it mean "All the workers in the Japanese music industry are fans of heavy metal music." or something like that?