In Pixar’s Cars 2, Mater’s profession before he becomes involved with international espionage is tow truck.
Mater is the rusty tow truck of Radiator Springs and Lightning McQueen’s best friend. In Cars 2, he travels with McQueen to the World Grand Prix and is mistaken for an American secret agent because of information gathered by real spies. His ordinary towing background contrasts with the sophisticated technology and undercover missions around him.
The film uses that contrast as a major source of comedy. Mater misunderstands spy terminology and situations, yet his honesty and unconventional behavior repeatedly help expose the plot involving Allinol and the criminal organization behind the races.
Mater is voiced by Larry the Cable Guy in the English-language films. His profession remains part of his identity even when the sequel places him in Tokyo, Porto Corsa, and London. He is not a mechanic or sheriff: those roles belong to other characters and settings in the Cars universe.