Mutators are special modifiers that give you more chances to earn Kill Coins while playing Global Ops!
When you enter a Global Ops Event, tap on the "i" button at the top left of the screen. If any Mutators are active for that Global Ops Event, you'll receive instructions on how to activate those bonuses. If you see the standard Global Ops instructions, then that particular Global Ops Event does not feature Mutators. Not all Global Ops Events have Mutators enabled.