Speed metal is an extreme subgenre of heavy metal music that originated in the late 1970s from New Wave Of British Heavy Metal (NWOBHM) roots. It is extremely fast, abrasive, and technically demanding to play.
It is usually considered less abrasive and more melodic than thrash metal, showing less influence from hardcore punk. However, speed metal is usually faster and more aggressive than traditional heavy metal, also showing more inclination to virtuoso soloing and featuring short instrumental passages between couplets.
Death metal is an extreme subgenre of heavy metal music. It typically employs heavily distorted and low-tuned guitars, played with techniques such as palm muting and tremolo picking, deep growling vocals, aggressive, powerful drumming featuring double kick and blast beat techniques, minor keys or atonality, abrupt tempo, key, and time signature changes, and chromatic chord progressions.
The lyrical themes of death metal may include occultism, horror, mysticism, mythology, philosophy, science fiction, and various forms of extreme acts