MEGADETH Dave Mustaine explains why these metal icons aren’t afraid to take risks  Megadeth’s latest album, Super Collider, celebrates 30 years in the metal trenches—and it will certainly satisfy the cravings of fans who feast on the band’s stock-in-trade: shock-and-awe thrash metal. But it may also confuse—and even anger—some die-hard headbangers. This is the most melodic record frontman Dave Mustaine has made in years, and there’s...