As the author does one really has to pry the culture apart. One thing the article correctly notes is that a lot of reactionary politics in metal rather happens in the rock-adjacent part of the genre. in Germany in particular neonazi politics is much more dominant in so called Rechtsrock than it is in 'metal proper'. Heavy metal, despite sharing the name, is a very different thing from the rest of the culture.

The other big one is Nordic metal / black metal. There's some truth to the presence of reactionary politics here, which is not that surprising to me because of its often pagan roots, which has always been a staple of the European far-right in particular. Although it's probably worth debating to what degree this is aesthetic rather than political and if that matters. I think it is often just alluring to people because of the taboo that is associated with Germanic and Nordic mythology in the German speaking world in particular. Similar to say, Wagner. While plenty of nationalists love Wagner's music and his association with Germanic culture, you can take an interest in it without turning into one.

However for the rest of the metal subculture and in particular practically lived culture at concerts, communities and so on I have to say I don't think there is an invasion of reactionary politics. Metalheads are some of the most anti-authoritarian and generally accepting people around.