While Henry Cavill has donned the cape of Superman in the DC Extended Universe, he has voiced interest in joining the Marvel Cinematic Universe, specifically saying that he would like to play Captain Britain. In an interview with The Hollywood Reporter, Cavill was asked if he were to make the jump over to Marvel with his version of the Man of Steel being on hold for the moment, which character would he want to play. Cavill pointed to the character Captain Britain, voicing his interest in providing a modern take for Brian Braddock like Chris Evans did for Captain America.
I’m never going to say a Marvel character that is already being played by someone else because everyone’s doing such an amazing job. However, I have the internet and I have seen the various rumors about Captain Britain and that would be loads of fun to do a cool, modernized version of that — like the way they modernized Captain America. There’s something fun about that, and I do love being British.
Captain Britain debuted in 1976 and saw Dr. Brian Braddock gain mystical powers from the sorcerer Merlyn and his daughter Roma, eventually becoming a member of the X-Men team known as Excalibur. Many of the character's stories revolve around magic, legends, and the multiverse, with the last of these things being something that Phase Four of the MCU seems to really be leaning with the likes of the Loki series and the upcoming Spider-Man: No Way Home.
Another possible hint to the character joining the ever-expanding film universe is that a character closely related to him from the comics recently made their debut. Dane Whitman, aka The Black Knight, showed up Eternals, played by Game of Thrones star Kit Harington, and is a character that has worked alongside Captain Britain in the comics. It could be possible that the champion of the British Isles is not too far behind.
Cavill has kept himself busy when not playing Superman, currently filming Netflix's Enola Holmes 2 and starring in fellow Netflix series The Witcher as the lead character, Geralt of Rivia. With such a focus on magic and legends, the Witcher actor likely fit right into the stories of Captain Britain. While Cavill has voiced his interest in playing the character, it is very possible that the version of Captain Britain, should the character appear in the MCU, won't be Brian Braddock as currently in the comics the title of Captain Britain is carried by his sister, Betsy Braddock. Brian has taken the name of Captain Avalon.
Whatever version of the character and whatever name Braddock takes, if he was to appear in the MCU, Cavill would be an exciting pick for the role.