Thrash metal (not trash!!) is a subgenre of heavy metal music, one of the extreme metal subgenres that is characterized by its high speed and aggression.

The origins of thrash metal are generally traced to the late 1970s and early 1980s, when a number of bands began incorporating the sound of the New Wave of British Heavy Metal (NWOBHM), creating a new genre and developing into a separate movement from punk rock. This genre is much more aggressive compared to its relative, speed metal. There is often significant crossover from one metal category to another, and the influence of non-metal genres, including classical music and jazz, is not uncommon.

The genre features a number of fast and rapid tempos, low-register, quick, complex guitar riffs, and high-register guitar solos. Palm muting and staccato are used in these tightly controlled riffs to create a "chugging" sound. Thrash guitar solos are almost exclusively played at high speed, as they are usually characterized by shredding, and use techniques such as sweep picking, legato phrasing, alternate picking, string skipping, and two-hand tapping. As with many other metal subgenres, thrash lead guitarists are often influenced by outside musical genres too, such as jazz fusion (Ex-Megadeth guitarist Chris Poland and Alex Skolnick of Testament) and classical music, such as Marty Friedman, has a lead style that could be grouped in the neoclassical shred genre.

The speed and pacing of the songs is what defines thrash metal. The music tends to have a visceral, propellant feel to it due to the often intense drumming, most commonly utilizing the snare drum on the 1/2 beat, or the 2nd and 4th beats of the measure. Frantic bass drum use is also common. Thrash drummers often use two bass drums. Many thrash drummers, such as Dave Lombardo, Nick Menza, Jürgen Reil, Gene Hoglan, Igor Cavalera, and Charlie Benante are revered as some of the "best drummers in rock music" due to their ability with the double-bass as well as adequately keeping time. Due to the genre's high speed, many thrash bassists use a pick to keep up with the other instruments. However, a few prominent bassists in the subgenre including Carl Peterson, Frank Bello, Greg Christian, Robert Trujillo, and the late Cliff Burton have shunned the use of the pick. Distorted bass (popularized by Burton and Lemmy) is not uncommon.

Themes worked in the genre include gore, life and death, society, and an array of other themes. But perhaps what thrash metal lyrics most often include is a nihilistic view of the society and the human being in general, for it working with warfare, brutal feelings supposedly hidden into human unconsciousness and visions of a possible future collapse of civilization (which partially overlaps with punk ideas, as this movement began a decade before). In contrast to many extreme metal genres to follow, thrash metal often focused on positive social issues, for instance environmentalism as was in the case of the band Nuclear Assault.

Well known bands for their importance in thrash music: Metal Church, Metallica, Overkill, Venom, Slayer, Megadeath, Testament, Exodus, Anthrax and others.