Gregarious would be a good word to describe Swerve. So would outgoing, enthusiastic, upbeat, joyfully irreverent, flippant, sarcastic, wise ass, troll, or "total pain in the aft," depending on which side of his weapons-grade mouth you happen to fall on and how long you've been listening to him use it. Swerve has a sense of fun and even whimsy that stands out from your run of the mill Autobots fairly dramatically. The little fellow may get on their nerves... he'll probably get on their nerves... But it'll always be with a smile, a laugh, and an epic level quip, making him a good bartender.
He is, however, also a menace to everyone within range of a gun in his hand - including himself - given his legendarily bad aim, as well as to anyone driving nearby because he's so easily distracted by just about anything that catches his attention. Despite this, he's quite intelligent and skilled as a metallurgist, analysing the properties of a material with unique sensors in his hands. When he gets caught up in a problem, he becomes almost laser-like in focus and intensity, going on quest after quest, both major and minor. Unfortunately, this generally leaves him just as distracted from any other tasks at hand and just as accident-prone as ever. He's almost always in need of some repairs, major or minor, because of it.
Now if only Prime could get him to not get easily distracted when receiving his orders too...
His alt-mode is a 4x4 Pickup Truck.