subphreeky said: 

 Hmmmm... I don't think you have to put out an album to be popular. Anyway I've heard that quite a lot about Testament being in the Big Four. In regards to Valhala, I've always heard about the big four: Anthrax, Megadeth, Metallica, and Slayer, and the big triad of Teutonic thrash: Destruction, Kreator, and Sodom. 

  
 what he said is bullshit now read what i have to say: 

 WHAT!!!!!!!!!!!! WTF i think you are one stupid mother fucker because first of all Metallica isnt thrash and neither is slayer. metallica is in a genre called creeping metal and slayer is in with speed. listen to slayers rifts they always change and never have a certian melody to fall back on. the four main thrash bands were  Exodus, Megadeth, Heathen, and Annihilator. and yes others include some of the bands you mentioned but there are way the fuck more that you left out that were very popular with the thrash genre.