Thanks to the Marvel Cinematic Universe, Captain America and Iron Man became the face of the Avengers for mainstream audiences. They also were the key figures on each side of the Civil War storyline and both played a key role in saving the world from Thanos. In the comics, the two men are just as important.
They were two of the earliest heroes in the Marvel Universe, Iron Man one of the first Avengers, and Captain America a war hero brought back after years on ice. They also became close friends, although they were often bitter rivals too. They were both heroes who were used to doing things their own ways, and while both men remained stubborn in their own ideals, they still shared a healthy respect for each other.
Captain America Wasn't An Original Avenger
While fans of the MCU saw Iron Man and Captain America as two of the founding members of the Avengers, that is not what happened in the comics. Instead, Iron Man was a founding member and Captain America didn't join until later.
Admittedly, Captain America was an early member, but he didn't join the team until Avengers #4 by Stan Lee and Jack Kirby. With that said, the team has retroactively considered Cap a founding member, even though Iron Man has on at least one occasion pulled rank over Cap.
Iron Man Said His Greatest Moment Was Finding Captain America
The Avengers formed when Iron Man, Ant-Man, Thor, and Wasp teamed up to stop Hulk, only to learn that Loki was the real enemy. Three issues later, they discovered a body frozen in ice and it turned out to be Captain America. Years later, Iron Man revealed how important that moment was.
This happened in Fallen Son: The Death of Captain America, and it took place after Cap died after Civil War. This was Cap's funeral, and Tony Stark admitted that the Avengers finding Captain America was the greatest day in his life.
Captain America Trained Iron Man As A Fighter
Captain America is a super-soldier with enhanced strength and durability, while Iron Man is a scientist who wears armor. This makes them both powerful, but Cap has one huge advantage over Iron Man. In a battle without the armor's weapons, Iron Man was a below-average fighter.
That all changed thanks to Captain America. Knowing that the Avengers needed Iron Man to be a skilled combatant, Captain America helped train him in one-on-one combat. In Iron Man #125, Cap showed how much Iron Man had to learn about fighting.
Captain America Knew He Couldn't Help Iron Man With Recovery
One of Iron Man's best storylines in comics was the "Demon in a Bottle" story by Bob Layton and David Micheline. In this story, Iron Man didn't have to beat a supervillain. Instead, he fought his own addictions.
In this storyline, Tony told Captain America that if he knew what was going on inside his head, he would know why he had to drink. Cap wanted to help, but dropped a bomb when he told Iron Man that his own father was an alcoholic, and he learned that he can't help until the alcoholic wants to be helped.
Captain America Was Against Iron Man During Armor Wars
Captain America and Iron Man have had several battles. The one everyone knows about was their fight in Civil War. However, they also fought years before and in that case, when Cap was on the government's side instead of Tony. This was Armor Wars.
In this story, Iron Man set out to retrieve all his armor and weapons from anyone who has them, including the U.S. Government. Captain America went to stop him and arrest him, but Iron Man was able to escape. Cap agreed to give him a chance to do the right thing, showing the respect they shared at the time.
Cap Quit The Avengers After Iron Man Killed Someone
Iron Man was a founding member of the Avengers and Captain America was not. Normally, people look to the two of them as co-founders when making decisions, but there was at least one time that Iron Man pulled rank.
Iron Man led a team of Avengers to kill the Kree Supreme Intelligence in Avengers #347. Captain America, the leader at the time, disapproved, but Iron Man pulled rank and executed the mission. As a result, Cap stepped down as the team leader and left the team for a time.
Captain America Trusted Iron Man To Find His Replacement
Captain America died after he surrendered to Iron Man at the conclusion of Civil War. This was hard on Iron Man, who wondered if it was worth it in the end. However, while Captain America and Iron Man were at war, the two never lost their respect for each other.
Even after everything, Steve Rogers wanted Captain America to continue and asked Tony to help him do that. Steve wanted Bucky Barnes to be the new Captain America, and even though Bucky was anti-registration, Iron Man respected Steve's wishes and gave Bucky the costume and shield.
The Two Got Married On An Alternate Earth
In a moment that mostly became Internet lore, Captain America and Iron Woman got married on an alternate Earth. This happened after the Civil War storyline and during Dark Reign, when Norman Osborn took over.
In Dark Reign: Fantastic Four #2, Reed Richards found a way to look at different Earths to find one where Civil War didn't end in tragedy. He found one - Earth-3490 - where there was no Civil War. Here Steve Rogers, Captain America, married Iron Woman, Natasha Stark.
Iron Man And Captain America Reconciled After Siege
After Civil War, fans were mostly horrified. However, Marvel decided to go back to square one after Siege ended. By this time, Thor hated Iron Man and things were not good for the Avengers. After Siege, the Heroic Age started and things finally got back to normal.
Norman Osborn was out of power and Steve Rogers had returned from the dead. In Avengers Prime, Thor, Captain America, and Iron Man finally rekindled their friendship and let the past remain in the past, all becoming Avengers again.
Iron Man & Illuminati Mind-Wiped Captain America
As much as Captain America and Iron Man remain friendly, the two have often butted heads and Tony Stark is not always the noblest and most honorable hero. The Illuminati was a group of heroes who worked behind the scenes to save the world, and they often failed.
When the Illuminati realized the Incursion was coming, they chose to attempt to destroy the other Earths. Iron Man brought in Captain America out of respect, but he didn't believe they should destroy the other worlds. Knowing the danger, Iron Man agreed to have Cap's mind wiped. This eventually was undone and Captain America set out to bring down the Illuminati.