Interestingly enough
Wiki says:
Heavy metal purists, also called "metal elitists", often show great distaste for more mainstream forms of heavy metal, such as glam metal and nu metal. Metal purists are most prevalent in the black metal scene, often rejecting bands for deviating from the "true" black metal sound.
A genre (pronounced /ˈʒɑːnrə/, also /ˈdʒɑːnrə/; from French "kind" or "sort", from Latin: genus (stem gener-)) is a loose set of criteria for a category of composition; the term is often used to categorize literature and speech, but is also used for any other form of art or utterance.
Genres are vague categories with no fixed boundaries, they are formed by sets of conventions, and many works cross into multiple genres by way of borrowing and recombining these conventions. The scope of the word "genre" is sometimes confined to art and culture, particularly literature, but it has a long history in rhetoric as well. In genre studies the concept of genre is not compared to originality. Rather, all works are recognized as either reflecting on or participating in the conventions of genre.
Genres are often divided into subgenres. Literature, for example, is divided into three basic kinds of literature, which are the classic genres of Ancient Greece: poetry, drama, and prose. Poetry may then be subdivided into epic, lyric, and dramatic. Subdivisions of drama includes foremost comedy and tragedy, while eg. comedy itself has subgenres, including farce, comedy of manners, burlesque, satire, and so on. However, any of these terms would be called "genre", and its possible more general terms implied.
To all the purists...I just have to say....metal is a subgenre of music....by your hypothesis, there are more people claiming metal to be a a degraded form of music and hence it must not be considered a form of music....dont unconsciously follow down the path u chose to avoid....just listen to everything!!!! Have your favourites...but a discussion of what is and isnt...is pointless...