Gigantour brings thrash-metal pioneer Megadeth, death-metal groups In Flames and Job For a Cowboy, black-metal band Children of Bodom and doom-metal rockers High on Fire to the Merriweather Post Pavilion for a show that's not for the faint of heart. Megadeth, the headliner, has had a successful and sometimes tumultuous career that has spanned more than two decades and yielded six platinum albums, seven Grammy nominations and more than 20 million albums sold worldwide. The event begins at 4:30 p.m. Saturday. Merriweather Post Pavilion is at 10475 Little Patuxent Parkway, Columbia. $40. Call 410-547-7328 or go to tick etmaster.com.