Metal
Origins
Metal grew out of heavy rock music, and it became popular in the late 60s. It's sometimes difficult to tell the difference between heavy rock and early metal due to the fact that one grew out of the other. Some early metal bands were inspired by rock ‘n’ roll and blues, as well as rock, so include fingerprints of these genres as well in their music.
Musical Fingerprints
Instrumentation: Vocals (aggressive/powerful), electric guitar, bass guitar, drums. Maybe a synth. Shredding style guitar playing.
Melody: Highly virtuosic riffs and guitar solos.
Tempo and time signature: Tempo usually fast. Multiple and less common time signatures were often used in later metal music.
Lyrical content: usually focused around darker themes.
Harmony: Primarily quite basic harmony. Some bands used modal harmony.
Technological Fingerprints
Much like Rock, Metal bands like to use, and exploit, the most modern technology available.
Large-scale tape machines allowed bands to create thicker ‘heavier’ textures.
Multimic’ing on drums.
Excess of everything in terms of distortion and effects.
Artists
Black Sabbath, Iron Maiden, Metallica