Iron Winter

Iron Winter is the slash ship between Tony Stark and Bucky Barnes from the Marvel Cinematic Universe fandom.

Captain America: Civil War
After being turned back to the Winter Soldier by Helmut Zemo, he finds himself having to fight Steve Rogers and Sam Wilson and ends up being surrounded by Joint Counter-Terrorist Centre agents. The Winter Soldier fights through the agents until he has to fight Tony Stark. Tony attempts to apprehend the Soldier with his Iron Man Gauntlet, which gave off shockwaves. The Soldier fought through these and attempted to shoot the Stark in the head, but was disarmed by Tony, who then got punched in the chest. After this, Sharon Carter and Natasha Romanoff came in to aid Tony and defeat the Winter Soldier, but failed as he overpowered them. By then, Tony had gotten away.

The next time they meet was during the fight at the airport in Leipzig, Germany. They did not exactly encounter each other again until Steve and Bucky escaped on the Quinjet.

Arriving at the Siberian HYDRA facility, Tony had followed them and established a short-lived peace when he had figured out Bucky's innocence. Helmut Zemo ruined this, though, as he revealed that the Winter Soldier had killed Tony's parents, Howard and Maria Stark.

The three have a fight, Bucky and Steve teaming up on Tony. Ignoring Steve's words of Bucky being brainwashed and tortured to kill his parents, Tony still attacks Bucky. After a while, Bucky almost escapes but soon gets trapped when Tony fires a missile at the hatch, preventing his escape.

Bucky is then put into a headlock by Tony, who questions him if he remembers killing his parents. Bucky responds by saying he remembers all of them until Steve managed to separate the two for a few seconds. Bucky uses Steve's shield as a weapon, teaming up with Steve and passing the shield around strategically.

Once Steve had been subdued, Bucky attacked Tony and attempted to rip out his Arc Reactor, but ended up getting his bionic arm blown up by Tony's repulsor. Steve then recovered and picked up his shield to disable Tony's Arc Reactor successfully. Steve picks up Bucky by his remaining arm and Tony, now incapacitated and no longer able to fight calls out Steve, stating that his Shield doesn't belong to him and he is undeserving of it because it was made by his father. Steve responds by dropping his shield, implying he's disowning his signature weapon, despite it being his primary artillery and walks away with Bucky.

Avengers: Endgame
As the avengers have departed, Tony and Bucky never interacted in this movie, due to Bucky also being one of the victims who were erased from existence when Thanos snapped his fingers and eliminated half of life, or what was publicly called the "Blip" in the Spider Man: No Way Home film. Rendering Bucky, and trillions of other as no longer existent for a span of five years, until the remaining Avengers went back in time and managed to collect the Infinity Stones from the past. Tony also loses his life in Endgame. But despite having no interactions, it's quite safe to assume they are no longer enemies and probably have a neutral relationship. Since Iron Man decided to give Captain America his shield back, and Bucky was one of the many people that was there for the funeral of Tony.

Avengers: Endgame

 * Bucky attended Tony's funeral.

Fanon
Iron Winter is pretty popular among MCU fans. Scenario where Tony bonds with Bucky by fixing his metal arm is common in fanworks.

On AO3, Iron Winter is the second most written ship for Bucky and the fifth most written for Tony. It is also the ninth most written ship in the Marvel Cinematic Universe tag. There are also about 20 works on fanfiction.net and 230+ results on Wattpad with the tag 'Winteriron'. Most of these fanfictions are fix-its, AUs, or some other variation.

Fandom
FAN FICTION
 * Bucky/Tony (Avengers Film) tag on FanFiction.net
 * Bucky/Tony (Marvel Comics) tag on FanFiction.net
 * Bucky/Iron Man (Avengers Cartoon) tag on FanFiction.net
 * Bucky/Iron Man (Avengers Cartoon) tag on FanFiction.net

DEVIANT ART

TUMBLR

Trivia

 * Robert Downey Jr. (Tony Stark) has given Sebastian Stan (Bucky Barnes) a kiss on the cheek before.

Variations

 * Stuckony refers to the ship between Steve Rogers, Bucky, and Tony
 * T'Stuckony refers to the ship between T'Challa, Steve Rogers, Bucky and Tony
 * Winterfamily refers to the ship between Peter Parker, Bucky and Tony (Peter as their son)
 * WinterIronFrost refers to the ship between Loki, Bucky and Tony
 * WinterIronPanther refers to the ship between T'Challa, Bucky and Tony
 * WinterIronWidow refers to the ship between Natasha Romanoff, Bucky and Tony