Black Metal is probably the most extreme subgenre of Heavy Metal.
The first spawns and records of this music were released in the early 1980's,
by bands like Venom, Bathory and Sodom. Their early appearance was in general
more raw, and their records of lower audio quality than typical Heavy Metal records at this time.
The first records featured mostly satanic, blasphemic and morbid lyrics.
Many todays Black Metal Bands still follow this "classic" path.
With the time, Bands and Black Metal itself evolved and started to feature more than just the typical, satanic, violent themes and the rather primitive musical appaearance. Black Metal bands like Bathory, added later new themes like paganism and nature, and Bathory formed new subgenres like Viking Metal. Bands like Endstille focus with their albums and lyrics mainly on World War I and II. Black Metal features within, alot of different interpretations, forms and sound layouts.
In general the typical identification schemes for Black Metal are: Guttural, inhuman vocals, low tuned guitars, repeating riffs, monoton sound, alot of reverb, dark and morbid layout and extreme lyrical themes like death, blasphemy, war and total destruction.
Real Black Metal has no intention in trying to be commercial sucessful. it is the pure opposite. Black Metal is anti commercial and not meant to be consumed by the brainless masses. Instead is the primary goal to shock the audience, let minds suffer, and make common subjects run away in fear. There is no intention into making the listener happy or feel good while he listen to the mind crushing Black Metal records. The contrary is the purpose.
The common subjects dont understand the art, dark and evil energy of Black Metal. They consider Black Metal just as a primitive, raw and loud kind music. But this so often mentioned as "primitive" music can be intense, complex and emotional like orchestral, classic music. It grabs and it throws you right into another dimension, a dark music realm, intense and destructive. A realm without any escape.