Is there a mission mode in combat arms

yes, but only in the Korean version, it is possible that nexon will release the campaign mode in a future patch for combat arms global.

New Answer---Yes mission mode or campaign mode is considered fire team mode and is like a campaign because , in Fire Team mode , there are objectives and you play with a team of players against computers , basically your enemies are computerized(computer controlled). There are four types of fire teams in combat arms , Cabin Fever , Desert Fox , Desert Thunder and Black Lung--currently in December 2010. If you want more info about fire teams in combat arms or any other info , I advise you to go to the combat arms wiki,(Combatarms.wikia.com).