Introduced in Star Wars (1977), Han Solo is indebted to Jabba the Hutt after the loss of valuable cargo.
On Tatooine, Solo accepts a charter to transport Luke Skywalker, Ben Kenobi, C-3PO and R2-D2 to Alderaan in his vaunted (and junked) Millennium Falcon spaceship for a payment which will help him clear the debt. But when the crew and passengers arrive at the planet's coordinates, they discover that Alderaan has been destroyed by the Death Star.
The Falcon is then captured and held within the battle station, however Han Solo, Chewbacca and his passengers evade capture by hiding in the ship smuggling compartments. While trying to find a way to escape Luke Skywalker discovers that Princess Leia Organa (Bond fans?) is being held captive aboard the station. Enticed by the likelihood of a large reward, Solo and Chewbacca help Skywalker rescue the princess and escape from the Death Star.
After delivering Skywalker, Leia and the droids to the Rebel Alliance, Solo and his Wookiee co-pilot receive payment for their services. Unfortunately the Millenium Falcon has been tracked to the Rebel Alliance moon base by the Death Star. The rebels plan to attack the space station and exploit a weakness in the space station's defenses. Solo initially does not want to get involved in the planned attack because,”What good's a reward if you ain't around to use it?” Solo leaves with his reward and the rebels attack the Death Star.
However, Solo has a change of heart and returns to save Luke's life during the film's climactic battle scene, ultimately enabling Luke to destroy the Death Star. For his heroics, Solo is presented with a medal and is appointed a Captain of the Rebel Alliance.
In The Empire Strikes Back (1980), Han Solo continues to assist the Rebels against the Empire.
Han once again risks his life to save Luke Skywalker by braving a snowstorm on the ice planet Hoth to rescue his wounded friend. When the Empire attacks the Rebel base, Solo transports Chewbacca, Leia Organa and C-3PO to Cloud Citywhere his old friend Lando Calrissian (Cloud City's administrator) operates to hide from Imperial agents.
When bounty hunter Boba Fett tracks the Falcon to Cloud City, Darth Vader forces Calrissian to help capture Solo who is then sealed in carbonite (that scene still hurts me) for delivery to Jabba the Hutt. Lando is able to free Vader's other captives but their rescue attempt of Solo fails and Fett is able to escape with Solo's frozen body.
During Return of the Jedi (1983), Han Solo is still frozen until Leia, Jedi Knight Luke and Lando infiltrate Jabba the Hutt's palace and free him but they're caught by Jabba before they can escape. When Jabba orders them to be executed, Solo helps Luke, Leia, and Lando in defeating Jabba and his henchmen before escaping and defeating Boba Fett.
Reunited with the Rebels, Solo is commissioned as a general. Along with Leia and Chewbacca, he goes to the forest moon of Endor and leads a team deactivating the force fields protecting the Empire's second Death Star, in which they are aided by the Ewoks while Luke fights the Emperor on the Death Star.
When the Death Star is destroyed, Solo sees Leia's concern for Luke and offers to step aside for the young Jedi to court her. However, Leia reveals to Han's surprise that Luke is her brother, and thus will obviously have no objection to his friend's relationship with her.
At the end of the classic film, Solo joins the Rebels in celebrating the destruction of the second Death Star and the Empire. At the end, he and Leia declare their love for each other while reuniting with Luke and Lando as well.