There is no pickup in the world that's going to make you sound like these guys. For one thing, they all use different pickups. Metallica and Zakk use EMGs. Steve, Joe, and Randy have all used different models of Dimarzios at different points in time.
EMG 81s or 85s, Evolutions, and FREDs are completely different pickups and it all depends on what you want. If you want sheer horsepower to burn, but digital effects friendly, controllable at any volume, the EMGs are peerless. If you want over the top shredding power with no brakes, the Evo is your best bet. If you want a pickup you can do anything with given the right amp and proper effects, go for the FRED.