It looks like it could be good. It kills me how metal is portrayed in pop culture, so I'm a little gun-shy. I saw the film Hesher and thought it must be so difficult when one is not a part of something to approach it with respect or understanding. In Hesher Gordon-Levitt was, to me, the opposite of what many fans are like; his performance was like a drunk cartoon to me.
Not that Sound of Metal looks that way, and I'm curious about the actor, about whom I have a good feeling. But I did have this feeling the music might be off in a way I'd have to actively distance. The term metal doesn't mean much, and to me is more of a signifier that one is trying to speak in a strategically overtly generic manner: by using it one is blanketly referring to an unbelievable number of sub genres, each with its own esthetic, completely different standards of taste and musicianship, loosely related by amounts of guitar gain (another dubious connection). A browse through metal-archives.com can give one an idea of how vast it really is.
I'm still curious to try Sound of Metal, but I've got so much ahead of it, it will be a while. Right now I'm hoping to see more of the Criterion Channel's collection of Robert Ryan movies. The first couple were fantastic!