There were a few different characters in The Lord of the Rings movie trilogy that put on the One Ring, and a couple characters in the books that put it on, though it wasn’t shown in the movies. How many characters put it on, how did they discover the Ring, and what happened to them after they wore it?
The Ring in The Lord of the Rings is a small, gold band. Despite its small and unassuming appearance, it is actually quite powerful and linked to a very evil spirit—its creator, Sauron. When mortals put on the Ring, they are transported to the Wraith-world, where spiritual beings like the Ringwraiths exist. After Sauron is defeated, his spirit also dwells in this world as Sauron’s lifeforce was bound to the Ring. The Ring (after Sauron’s initial defeat in the Second Age) can change its size to fit any creature who wears it—after that creature has claimed ownership of it, of course.
The Ring has a very strong pull, and it almost has a life of its own and will do anything to get back to its master. However, this is most likely just Sauron (who is essentially trapped in the Ring) trying to seduce those around it with tempting things like power, status, and riches. Sauron is a great manipulator, and uses the desires of the wearer of the Ring to convince them to do his bidding. The Ring appears to be innocent and ordinary to those who are not drawn to it, that is until its inscription is revealed by fire. This is why Gandalf was unable to detect the Ring until after Bilbo’s birthday party.
Sauron was the creator of the Ring, so he is the one who wore it first. It gave him great strength, and because Sauron’s power was finite, locking it into the Ring allowed him to have infinite power. Sauron disguised himself as a fair being similar to an Elf, and gave himself the new name of Annatar bearing the title Lord of Gifts. He went to the Elves and pretended to show them how to make magical rings which could be used for good. But they were fooled by Sauron, for the magic the rings possessed was a dark magic. And in secret, Sauron forged another ring—The One Ring—which was capable of controlling the wearers of the other Rings of Power. In The Last Alliance of Elves and Men, Sauron was defeated by Isildur who cut the Ring from Sauron’s hand and instantly claimed it for himself. He became the new Ring Bearer.
After defeating Sauron, Isildur was the next being to wear the Ring. The Ring was precious to Isildur, though he bought it with a great pain. He claimed it would be an heirloom to his family. Though the Elf named Elrond (Arwen’s father) tried to get Isildur to cast the Ring into the fires of Mount Doom, Isildur was transfixed and corrupted by the Ring, and he kept the Ring for himself. As Elrond said, the world of Men was weak, and the war should have ended that day—but evil was allowed to endure. Isildur got what was coming to him though, as during an Orc ambush, Isildur put on the Ring to escape (while abandoning the other Men he was with). But the Ring betrayed Isildur. When wearing the Ring, mortals become invisible. Isildur became invisible and tried to swim across a river, but the Ring abandoned him and grew in size—causing it to fall off Isildur’s finger, making him visible again. He was shot with several Orc arrows and killed.
The world thought the Ring had been lost, and after thousands of years, the legend of the Ring became a myth. That is until one day, when Déagol (Sméagol’s cousin) found the Ring in the riverbed of Anduin. Sméagol demanded the Ring as a birthday present, but they were both instantly captivated by the Ring. During the two Hobbits’ struggle for the Ring, Déagol handled the Ring briefly. But he was killed by his cousin, who then claimed the Ring—calling it his precious. Sméagol became the most notable Ring Bearer, as he was in possession of the Ring for 500 years. The Ring gave to him unnaturally long life, but he was cast out from society. Living in caves and underground in isolation and in possession of the manipulative Ring, Sméagol became something of a monster. The Ring, too, abandoned Sméagol who was then known as Gollum.
The Ring was picked up next by Bilbo Baggins—a Hobbit of The Shire. He kept the Ring for 60 years, never truly knowing its purpose or importance. He just thought of it as his precious and nifty, magical, invisibility ring. The Ring extended Bilbo’s life and prolonged old age. But when Bilbo decided to leave The Shire for one last adventure, he left the Ring behind for Frodo. Though he struggled with leaving it behind, Bilbo was one of only three beings to ever willingly give up the Ring. The next creature to wear the Ring was Frodo Baggins. In the books, Frodo kept the Ring tucked away and hidden for 17 years before heading off on his quest to take the Ring to Rivendale. Throughout the trilogy, the Ring’s burden on Frodo became stronger as they got closer to Mordor. Frodo was unable to let the Ring go, but because of destiny and an altercation with Gollum, the Ring was destroyed. Frodo did feel some instant relief when the Ring was finally gone, but he never fully recovered from the events and ended up leaving Middle Earth at the end of Return of the King.
Though Gandalf never wore the Ring, he did handle it a few times while inspecting it to see if it was indeed the One ring. Though he is not in the movies, the character Tom Bombadil was one of the few to ever wear the Ring and give it up willingly. Frodo took the Ring to Tom, allowing him to handle it, and the character even put it on briefly (without becoming invisible). Just as quickly, he handed it back to Frodo without a struggle. And lastly, the final temporary Ring Bearer in The Lord of the Rings was Samwise Gamgee. Sam carried the Ring for two days after Frodo was attacked by Shelob, and in the books he even wore it briefly. But his humble and good-natured soul was able to resist the temptations of the Ring, and he gave it back to Frodo willingly without hesitation.