Oh Regina Malissima Germanica Mea,
you're right, "Blechbläser" is not the word you're looking for. A Blechbläser is indeed a person playing a brass instrument. The translations you are seeking are:
heavy metal - Heavy Metal
metal - Metal
That's all!
"Heavy Metal" is occasionally used as a generic term for all genres of metal music. But usually - especially among metal-listeners - "Metal" is used as the generic term. In both cases you don't add "Musik" - "metal (music)" is just "Metal". By the way, the pronounciation is the same as in English - the words were simply imported from English.
Some examples are:
"Hallo. Ich bin die allerböseste Königin und höre gern Metal."
"Metal ist meine Lieblingsmusik seit ich drei Jahre alt war."
"Nu Metal ist gar kein richtiger Metal."
"Meine Nachbarn mögen keinen Metal. Das sind Vollpfosten und Spacken!"
Cheers!
Markus