The Avengers are some of Marvel's most prominent heroes, working to protect the entire world. But sometimes, they end up recruiting members of other teams -- notably including a distinct number of mutant heroes from the X-Men. Although they've occasionally recruited mutant adjacent figures -- such as Deadpool, Quicksilver, and Scarlet Witch -- they've also fully convinced former members of the X-Men to fight alongside them -- at least for a little while.
Now, we're taking a closer look at some of the most noteworthy heroes who've spent time as members of both teams at one time or another.
BEAST
Beast was one of the founding members of the X-Men, who eventually left the team and experimented on himself -- resulting in his blue furry form. He ended up joining multiple other teams for a period, including the Defenders and the Champions. But his most prominent spot on another team came in Avengers #137 by Steve Englehart and George Tuska. With their ranks reduced by recent events, the Avengers put out an open call for new members -- which Beast volunteered. After proving himself in battle, Beast became a major reoccurring member of the team for years.
NAMOR
Namor has long been one of Marvel's greatest wild-cards, going from established ally to heroes like Captain America and the X-Men (even joining the group for a period) to fierce rivals to the Fantastic Four and Black Panther. During a tumultuous period of his life though, Namor ended up joining the team at Captian America's request in Avengers #262 by Roger Stern and John Buscema. He was eventually joined with his then-wife, Marrina. However, Marriana would later die in service to the group, leading a despondent Namor to leave the team.
WOLVERINE
After Avengers Disassembled, Captain America and Iron Man were forced to recruit a new team. Iron Man's insisted in New Avengers #6 by Brian Michael Bendis and David Finch that Wolverine be admitted so the team could have someone who could have a ruthless outside perspective. Captain America was initially wary of Wolverine's history, but Logan ended up forging surprisingly close relationships with the Avengers -- even fighting alongside the Avengers against his more classical affiliation to the X-Men in AvX. Since then, he's become more committed to Krakoa over the Avengers, however.
STORM
Storm has long been one of the X-Men's most high-profile leaders. But after marrying Black Panther, Storm became increasingly prevalent across the Marvel Universe. Years after working with the Avengers on a mission, Storm and her husband briefly served alongside the Earth's Mightiest Heroes in Avengers #19 by Brian Michael Bendis and Daniel Acuña. However, her stint on the group was short-lived -- with Storm leaving the team due to the events of AvX, and Black Panther breaking off their relationship after Namor's attack on Wakanda.
THE UNCANNY AVENGERS
Uncanny Avengers #1 by Rick Remender and John Cassaday saw Captain America try to reform the Avengers with a more mutant element following the war between them and the X-Men, to help bridge the gap between the mutant population and the human heroes. This resulted in Wolverine and a number of other mutants being invited to the group -- including Sunfire, Rogue, and Havok. Havok became something of a leader for the team, but their time together resulted in a number of dangerous situations that resulted in the dissolution of the group after preventing the possible future of Planet X. In later incarnations, Rogue led the team, which counted X-affiliates Cable and Deadpool among its ranks.
SUNSPOT & CANNONBALL
Sunspot and Cannonball were both prominent members of the New Mutants, and major mutant heroes. Although they initially tried to retire from heroics, they changed their tune quickly when they were offered positions on Captain America's restructured team in Jonathan Hickman and Jerome Opeña's Avengers #1. They quickly adjusted well to the group, each taking huge steps in their lives. Cannonball fell in love with his teammate Smasher and ended up having a child with her, while Sunspot became a prominent member of the team and even a leadership role in his own Avengers rosters.
DAZZLER
Coming out of a difficult place in her life after being replaced publicly by Mystique, Dazzler was one of the heroes approached by Singularity following the events of Secret Wars to form a team in A-Force #1 by G. Willow Wilson and Jorge Molina. She was a powerful member of the group, and was even briefly killed during the event but was quickly restored to life -- but the dissolution of the group due to the events of Civil War II and Inhumans vs. X-Men resulted in Dazzler leaving the team and even trying to retire from active heroics for a time.