Music can be and in practice is vector for far-right propaganda too. Or I guess far-left, except I knew about neonazi bands when I was younger and did not knew about communist bands. By neonazi bands I mean bands whose lyrics propagate those ides. Distinction without difference in this case, basically.

It was not metal, it was rock in that case. But here, those metal bands were also expressing their ideas and opinions in their songs.

There was such a thing as disproportional moral panic around metal in USA. And there was also such a thing as metal bands actually being like that. It is like ... there was satanic moral panic where a lot of innocent people ended up suffering. And then there was real world child abuse going on too.