annie
metal maniac
I would say Venom and Motorhead had that first sound of speed/thrash metal. But it's just an endless discussion that will lead to nowhere.
That is correct, it is referred to as "proto thrash". According to BBC's "Seven Ages of Rock", Metallica started thrash metal with "Kill 'em All" and was the first of the so-called "big four" thrash bands - Metallica, Slayer, Anthrax, and Megadeth.