Thor is an Asgardian god of thunder and a powerful warrior in Asgard. His rival is his adoptive brother Loki. He is one of the first five heroes who founded the Avengers after Graviton's defeat.
The Wrecking Crew, trying to steal a piece of Stark Industries technology, are confronted by a squadron of police, whom they easily defeat using their powers. When Jane Foster arrives to treat the wounded, she is surrounded by the Crew, who start to advance on her when one of them is knocked back by a powerful blow. Thor appears, revealing the blow to have been his trusty hammer Mjolnir, which he had thrown at the Crew member and then recalled to his hand. Instructing the 'mortals' to stand back, he proceeds to single-handedly fight, and subsequently defeat, most of the Crew. When their leader takes Jane as a hostage, Thor expresses his disgust and asks if he has any honor. When Wrecker says no, Thor uses Mjolnir to attack him from behind, freeing Jane. As they are getting acquainted, with Thor asking her why she risks her life if she is mortal, they are interrupted by Heimdall, who says Thor is desperately needed in Asgard. Saying goodbye to a dumbstruck Jane, Thor flies onto the portal, leaving her alone on the pier.
When Thor arrives in Asgard, he is informed by Heimdall that the Frost Giants are marching towards Odin's throne. Since the Odinsleep is almost upon him, the King is weakened, and must rely on his warriors to stop them. Expressing frustration at not being able to help Thor due to his duty to defend the Bifrost Bridge, Thor tells him that he will fell a Frost Giant in his name. Thor then goes to confront the Giants.
He arrives at the scene of the fight just as one of the Giants is about to kill Sif. He breaks the creature's axe just as it is about to crush the female Asgardian, then confronts another Giant who is armed with a sword. As they battle, causing massive property damage to Asgard in the process, Odin sees through his ravens that Thor has arrived and breathes a sigh of relief. Thor continues to battle the Giants, and is about to finish them off when he is suddenly frozen by an unseen foe. He easily breaks free, but is pummeled by the remaining Giants. Just as one is about to bite his head off, Thor comes to and calls Mjolnir to him, just barely escaping the Giant's teeth. He then proceeds to defeat the Giants with a massive bolt of lightning.
As he surveys his victory, Thor is suddenly attacked from behind by his evil step-brother, Loki. Thor, seeing who attacked him, pleads with Loki to return to the person Thor once knew, but the God of Evil simply laughs at him, telling him he had his chance to pick sides, and lunges with his spear. Using Mjolnir, Thor fights his brother, and gains the advantage. He is about to finish Loki off with a huge blast of energy, when Loki simply vanishes. Proclaiming that Loki cannot beat him, Thor is again attacked from behind by Loki, who tries his best to stop Thor. Having had enough, Thor simply deflects his brothers attacks, and captures Loki, bringing him before Odin.
Odin is heart broken and infuriated by Loki's continued attempts to overthrow him, his own father, but Loki yells that Odin is not his father. He rants on about Odin being a liar and king of fools, but he pushes Odin too far, who banishes him to the Isle of Silence. When the deed is done, Thor approaches Odin, who tells him it is almost time for the Odinsleep, and that Thor has much to prepare. Thor, however, says that Balder and Sif will be there to defend him, while he goes back to attend Midgard. Outraged, Odin tells Thor that Asgard is his responsibility, not Midgard, but Thor rebuffs this, stating that he will not be apart of Odins game any longer. He accuses his father of keeping everyone under his heel, and that he copuld have stopped Lokis attack before it even happened. Just as Odin is about to lash out at him, Thor says that he will always be there to defend Asgard, if it needs it, but that he will see to Midagrd until then. He storms out, with Odin allowing his son to leave. Thor expresses some regret to himself over his actions, but remians firm in his belief that Earth is where he is neded the most. With that, he flies off back to Midgard, failing to notice that someone was watching him as he left.
Forming the Avengers
Thor is observing the city, and also follwoing Jane Foster, when he is approached by Balder. The two exchange happy greetings, but when Thor asks him why he is there, he sees the sadness in Balder's eyes, and asks who sent him instead. Balder says that Odin wants Thor to return home to Asgard, to defend it while Odin sleeps. Thor, however, refuses, which makes Balder question why Thor stays on Midgard. Thor says that he is needed there more than Asgard, since they fighting in Asgard is meaningless, and everything that happens on Earth is not. They are interrupted by sirens, and Thor sees Jane Foster tending someone who is hurt. However, a car bounces off of another car, which had previously been in an accident, and is about to crush her when Thor swoops down and saves her (Balder returns to Asgard off-screen). Expressing gratitude, Jane asks Thor if he had been following her, to which he shyly says yes, because she intrigues him.
The two of them go to a cafe, where they discuss their individual lives. Thor, who is attracting many glances and stares from passer-byes and others at the cafe, tells her about Odin and the Odinsleep. Hearing that his world is in danger while Odin sleeps, Jane tells Thor he should go back. When he says that he is needed on Earth (in a funny, stubborn way) Jane tells him that the mortals have been fine without him before due to their own heroes, and that it will be ok for a week. Just as it seems Thor might reconsider and go back home, there is an explosion. Asking Jane if she was so sure that Earth would still be there, Thor takes off to investigate the disturbance.
Thor is the first of Earth's heroes to confront the mad and very powerful Graviton, and is the first to witness his gravity-bending powers, which affect even the mighty Asgardian warrior. However, not one to back down, Thor continues to fight, until he is sent beneath the ocean by Gravitons power. He remains buried beneath the sand until the other heroes of Earth arrive, and distract Graviton enough for Thor to free himself. Rejoining the battle, Thor teams up with Iron Man, Ant-Man and Wasp in an attempt to stop Graviton. When Graviton lifts a huge portion of New York, which he is going to use to destroy the rest of the city, Thor uses Mjolnir to stop him, then flies down to catch the huge portion of earth and prevent it from causing a huge tidal wave which would have killed thousands. When they are all subdued by the insanely powerful villain, the Hulk arrives to aid them, and the battle shifts in their favor. In the end, after Hulk beats up Graviton, Wasp continues to sting him, Giant Man throws a huge ship on him, and Iron Man weakens him with a Uni-Beam, Thor unleashes his full power against the villain, and strikes him with a huge blast of lightning and magic, finally bringing the foe down (however, Wasp is the one to render him unconscious with a final sting when Thor's attack is done). After their victory, Thor group-hugs the informal team, but then S.H.I.E.L.D. arrives to re-capture the Hulk, who had been freed from the Cube along with most of Earth's villains.
As Hulk is about to attack, the others stand up for him, Thor included, and Iron Man says that the Hulk is as much of a hero as the rest of them were. Then, Iron Man asks the other four to join him as a team to bring down the remaining villains. When they all agree, and Wasp comes up with a name for the group, the Avengers are officially formed.