What if Dave Mustaine stayed in Metallica?

Anyone even remotely familiar with Metallica's story knows that Dave Mustaine, founder of Megadeth, was their original lead guitarist.

Peace sells, but who's buying?

It's hard to believe that the best albums of the thrash / speed metal genre, Metallica's Master of Puppets, Megadeth's Peace Sells, and Slayer's Reign In Blood, all came out twenty-five years ago.