Warning: SPOILERS for Superman & Lois Season 1, Episode 7 - "Man of Steel".
Superman & Lois' shocking revelation that the Stranger AKA Captain Luthor (Wolé Parks) is really John Henry Irons means that the Arrowverse now has two characters with claim to the codename Steel. Of course, the Arrowverse already had a Steel: Nate Heywood (Nick Zano) on DC's Legends of Tomorrow. However, the two men of Steel couldn't be more different.
Legends of Tomorrow's Steel is based on several characters named Steel in DC Comics. The Steel, real name Henry Heywood, was a cybernetic superhero introduced in Steel: The Indestructible Man in 1939. The second Steel was Henry's grandson Hank Heywood, who was introduced as part of a revamped lineup of the Justice League of America in the early 1980s. However, Legends of Tomorrow's Nathaniel Heywood is a revamp of Nathan Heywood AKA Citizen Steel, who was part of the relaunched Justice Society of America comics in 2007. Meanwhile, John Henry Irons became arguably the most popular DC superhero named Steel when he was introduced after The Death of Superman event in the early 1990s. There was even a Steel movie starring Shaquille O'Neal as John Henry Irons in 1997, which has largely been forgotten. Unlike the Steels with the surname of Heywood who were cyborgs or have organic metal skin, John Henry Irons forged a cybernetic suit and hammer to give him powers to rival Superman himself.
John Henry Irons' unexpected introduction to the Arrowverse was a genuine thrill since the hammer-swinging, armored version of Steel is a major DC hero that Superman & Lois' fans were led to believe is a villain. Irons is from another Earth in the Multiverse and he watched his wife, Lois Lane (Elizabeth Tulloch), murdered by an evil version of Superman (Tyler Hoechlin). As the Stranger, Irons left his planet to stop Earth-Prime's Superman from going down the same path. However, fans were swerved from the beginning of Superman & Lois since Irons' A.I. refers to him as "Captain Luthor". Naturally, everyone including Lois and Clark, assumed that Irons was an alternate universe Lex Luthor. But the truth turned out to be a jaw-dropper that was much impactful.
Nate Heywood's Steel has always been a hero and he's now one of Legends of Tomorrow's longest-serving time-traveling adventurers. For his part, John Irons is ostensibly a villain who wants to kill Superman, but his motivations are more complex and interesting. Irons really wants to avenge his world and the daughter he left behind, Natasha (Tayler Buck), who may or may not be alive. In a way, Irons is trying to save Earth-Prime while trying to avenge his world and his version of Lois. Since the Stranger isn't a Luthor after all, it means there's a chance that John could see the error of his ways and eventually become Superman's ally like they are in the comics.
It remains to be seen whether or not John Henry Irons will adopt the codename of Steel. If and when he does, it will be fascinating to see how that affects Nate, who inherited the codename from his grandfather, Henry Heywood AKA Commander Steel (Matthew MacCaull), who was a member of the Justice Society of America. Given Nate's generally easy-going nature, he may not mind another Steel in the world. After all, there have been many superheroes named The Flash and Superman in the Multiverse and, as a time-traveling historian, Nate welcomes all possibilities.
Both Superman & Lois and Legends of Tomorrow will return for new seasons in fall 2021 and, in addition, The Flash will begin mini-crossover events for its season 8. Now that the safety protocols caused by the COVID-19 pandemic are starting to ease, it opens the door for more potential Arrowverse crossovers. Indeed, Lois finally mentioned the Multiverse after weeks of Superman & Lois behaving as if the wider Arrowverse doesn't exist. It's possible that Legends of Tomorrow's Steel could meet John Henry Irons' Steel from Superman & Lois down the line, which would be a fun encounter for fans of both men of Steel to hopefully look forward to.