Lightning is running in the Dinoco 400 to win the Piston Cup, with the incentive that the winner would be the replacement for Dinoco's old mascot, Strip Weathers, who was retiring. However, during the race, he denies tire changes from his pit crew, requesting only gas. But about 100 yards from the finish line, his back tires blow out. Rather than winning the race, he barely manages a tie with Strip Weathers and Chick Hicks. His pit crew quit on him after he tells "Not Chuck", one of his members, to get out of the camera shot. Strip Weathers (also known as "The King") admonishes him for his overconfidence and lack of teamwork, but Lightning does not listen because he is lost in thought about the joys of working for Dinoco. Afterwards, he is forced to go into his sponsor Rust-Eze’s (a company that sells a rust-cleaning product) tent, which is full of rusty old cars, which Lightning hates. He then has a talk with his agent Harv, who explains how he got tickets for Lightning to give to his friends, but Lightning is unable to respond to this due to the fact that he has no friends.

Now on his way to the tie-breaker race in Los Angeles, Lightning orders his driver Mack to drive all night to get the sponsorship, but he inevitably falls asleep. Lightning ends up lost in a little ghost town called Radiator Springs and after tearing up their main road, he is sentenced to community service to repair the road.

While he is in town, he meets a selection of cars, most notably Doc Hudson and Sally Carrera. Although at first rude to Doc, McQueen does find out about his past as a Hudson Hornet who won 3 Piston Cups until a devastating crash put him out of season which caused him to be replaced by a rookie. With Sally, the two take a drive and McQueen begins to learn about Radiator Springs' past and how it used to become a landmark until the interstate highways took over. As a result, he soon comes to realize how arrogant and selfish he has been and that there is more to racing than just winning and what people in the real world have gone through in their lives. He also makes friends with every car in town, especially Mater, a rusty tow truck who chooses him as his best friend, even going Tractor Tipping with him and showing his signature backwards driving move. At the end of the film, Lightning, Chick Hicks, and The King vie for the Piston Cup in a tiebreaker race in Los Angeles. During the race, he thinks about his new friends which cause him to spin out off the track but regains confidence when he finds out that Mater, Luigi, Guido, Fillmore, Sarge, Sheriff, Ramone, along with Doc Hudson who has acted as McQueen's new crew chief arrived to support him. McQueen even tried the new tricks his friends taught him in the race when Chick Hicks plays dirty such as driving backwards and doing Doc Hudson's signature move when he goes out on the grass once more.

Lightning is about to win the race by several car lengths when The King is wrecked badly by Hicks. Lightning is reminded of Doc Hudson's horrible crash that brought an end to his career and unable to bear the thought of something similar happening again, he abruptly skids to a stop just in front of the finish line, allowing Chick to win the title. Humbly accepting his loss, Lightning heads back down the track to save The King and help him across the finish line to give him a respectable finish for his final race, coming in third place, the best finish for him much to the crowd's amazement. As McQueen pushes the injured racer to the finish line, The King points out to Lightning that he sacrificed his Piston Cup win to save him, only for Lightning to say that a grumpy old race car once told him that "it's just an empty cup.", having learned that friendship is important.

Impressed by his good sportsmanship, Tex Dinoco offers the contract to be their mascot to Lightning rather than the now unpopular Chick Hicks, but Lightning turns it down, saying he needs to complete his contract with Rust-Eze, the company who gave him his big break, first. He then sets up his permanent racing headquarters in Radiator Springs, drawing attention back to the little town and making it popular again, and simultaneously returning it to the map. In the process, Route 66 forevermore once again becomes a historical tourist attraction.

https://disney.fandom.com/wiki/Lightning_McQueen

At first, Lightning is self-centered, perfectionist and overconfident. He believed he could win the Piston Cup on his own without help from any pit crews or coach, without cheating, like Chick Hicks. He was so full of himself to the point where he claimed he didnt need any friends and couldnt get anyone's names right. Because of his attitude towards people, he turned out to be rather friendless and became lonely

Later, Mcqueen is transformed into a more sympathetic, understanding, and selfless racecar driver during his time in Radiator Springs on Route 66. During the final race, his new personality made him change his ways when he decided to accept defeat by forfeiting the Piston Cup so he can help Strip Weathers finish his last race, realizing that helping others is more important than winning even if it allowed Chick Hicks to win. He has since learned to enjoy making new friends and to treat others with respect.