Source : The Metal Crypt
•Traditional - Traditional heavy metal, also known as classic metal or simply heavy metal, is the seminal genre of heavy metal music before the genre "evolved and splintered into many different styles and subgenres."
•Thrash - Thrash metal is a subgenre of heavy metal that is characterized by its fast tempo and aggression.
•Power - Power metal is a style of heavy metal music combining characteristics of traditional metal with speed metal, often within symphonic context.
•Progressive - is a subgenre of heavy metal, which blends the powerful, guitar-driven sound of metal with the complex compositional structures, odd time signatures, and intricate instrumental playing of progressive rock.
•Death - is an extreme subgenre of heavy metal. It typically employs heavily distorted guitars, tremolo picking, deep growling vocals, blast beat drumming, minor keys or atonality, and complex song structures with multiple tempo changes.
•Black - is an extreme subgenre of heavy metal. It often uses fast tempos, shrieked vocals, highly distorted guitars played with tremolo picking, blast beat drumming, and unconventional song structure.
•Doom - is an extreme form of heavy metal music that typically uses slower tempos, low-tuned guitars and a much 'thicker' or 'heavier' sound than other metal genres. Both the music and the lyrics intend to evoke a sense of despair, dread, and impending doom
•Grindcore - is an extreme genre of music that started in the early- to mid-1980s. It draws inspiration from some of the most abrasive music genres – including death metal, industrial music, noise and the more extreme varieties of hardcore punk.
•Gothic - is a subgenre of heavy metal music. Gothic metal combines the aggression of heavy metal with the dark melancholy of gothic rock. The music of gothic metal is diverse with bands known to adopt the gothic approach to different styles of heavy metal music. Lyrics are generally melodramatic and mournful with inspiration from gothic fiction as well as personal experiences.
•Folk - is a sub-genre of heavy metal music that developed in Europe during the 1990s. As the name suggests, the genre is a fusion of heavy metal with traditional folk music. This includes the widespread use of folk instruments and, to a lesser extent, traditional singing styles.
•Viking - is a subgenre of heavy metal music characterised by its galloping pace, keyboard-rich anthemic sound, bleakness and dramatic emphasis on Norse mythology, Norse paganism, and the Viking Age.
•Symphonic - is a term used to describe heavy metal music that has symphonic elements; that is, elements that are either borrowed from classical music or, as with progressive rock music, create a style reminiscent of it, e.g. operatic female lead vocals; instrumentation that includes acoustic guitars and different types of keyboards instead of relying solely on electric guitars; asymmetrical meters such as 5/4 and 7/8, and classical thematic material in addition to characteristically heavy metal power riffs.
The above are really just the main sub genres but they are a lot more sub genres of heavy metal, some of which are only a few years old while some are very old.
Here are a few more
- Pirate metal
- Christian metal
- Nu Metal
- Glam Metal
- SID Metal
- True Metal
- Pop/Party Metal
- Stoner Metal