Here are 15 bands that are considered pioneers of thrash metal.

We know you know that Metallica, Slayer, Megadeth and Anthrax are considered the "Big 4" of thrash, but who were the pioneers of the genre that inspired them in the first place?

It's pretty clear that thrash is defined by aggression and very fast instrumentation. But when you compare those four aforementioned groups, in addition to all the other non-"Big Four" thrash groups such as Overkill, Testament and Exodus, there are actually a lot of differences in their sound and style.

They would all go on to influence metal bands in very different subgenres. With that, where was thrash derived from? Which bands were responsible for the arrival of this new category of metal?

The two main components that would contribute to the rise of thrash were the New Wave of British Heavy Metal groups — such as Iron Maiden and Judas Priest — and the punk groups — the Ramones, the Misfits — of the mid to late 1970s. The rapid playing, the attitude and the anti-establishment messages of both groups played a pivotal role in the emergence of thrash.

READ MORE: The Best Cover Song by 11 Big Thrash Metal Bands

There are plenty of other bands that don't quite get the same recognition for their influence on the genre, so we've compiled a list of names that deserve to be noted. Scroll through the gallery below to see 15 bands who are considered pioneers of thrash. 

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15 Bands Considered Pioneers of Thrash Metal

To see the albums the thrash pioneers helped influence, check out the 50 greatest thrash albums of all time ranked below.

Top 50 Thrash Albums of All Time

The 50 best thrash albums of all time.

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