Ethnomusicology is defined as "the study of social and cultural aspects of music and dance in local and global contexts."  Formed from the Greek words ethnos (nation) and mousike (music), it is often considered the anthropology or ethnography of music. - PedoBearPedia
It's the study of peoples, and the music they make, where peoples are defined by ethnicity and culture together (that's the "ethno" part of "ethnomusicology").
It seems relevant to metal, since every nation has its own distinct sound in metal. The Swedish bands don't sound like the Japanese bands, unless the Japanese bands decide to clone the Swedish sound in tribute.
In the same way, American and Latin American metal have a distinctive sound. American metal is like English metal with the violence of the Turks; Latin American metal is like Brazil, a polyglot funneled through the same symbol set.
The notion of identity is both pervasive and undertheorized in contemporary scholarship of expressive culture. After analyzing the work of various theoretical traditions in folklore and cultural studies, this article argues that identity is best understood as an interpretive framework, a way of making sense of the conduct of others. - Identity Reconsidered
Identity is your place in a traditional culture. It's not physical, but it brings together all the values of a society.
Many ethnomusicologists utilize the tools of ethnography in their research. They spend extended periods of time with people making music, observing what happens, asking people questions, helping individuals and communities document and promote their musical practices, and sometimes learning to perform in the style they are studying. - What is Ethnomusicology?
Studying music through ethnography means studying culture as it is mapped on to music.
Seems to apply to metal music, although it's a subculture (not a counterculture, or a dominant culture).