The film is expected to focus on its titular character balancing his Kryptonian heritage with his human upbringing.
Gunn has said, external it starts “right in the middle of the action”, with Superman already in existence, and “takes place over a short amount of time”.
He has also said there’s “plenty of humor in it” – although less than in some of his previous films like Suicide Squad or Guardians of the Galaxy.
“People like Rachel are so funny and David is very [funny as well], so there’s humour in it,” he said.
“But it’s trying to create something that is grounded, but also it’s an incredibly fanciful world, it’s fantasy, it’s taking from other things like Game of Thrones, where it’s this universe where superheroes actually exist. What are they like? There’s a magic there that’s undeniable.”
Corenswet’s Superman is seen wearing the hero’s famous red trunks – but Gunn said he was “on the no-trunks team for a long time” before filming started, until the star convinced him otherwise.
“One of the things David said is that Superman wants kids to not be afraid of him. He’s an alien. He’s got these incredible powers. He shoots beams out of his eyes, can blow the truck over.
“He’s this incredibly powerful, could be considered scary individual and he wants people to like him. He wants to be a symbol of hope and positivity.
“So he dresses like a professional wrestler, he dresses in a way that makes people unafraid of him. That shows that. And I was like, that really clicked in for me.”