James Gunn has admitted he's "miserable" after making 'Superman'.

The 58-year-old director is currently working on the post-production of the upcoming DC blockbuster as it nears its July 2025 release, and Gunn, 58, has admitted he has been left overwhelmed by making the movie.

In an interview with io9, he said: "I'm miserable. Really I'm miserable.

"But hopefully it's for the greater good."

Gunn - who is co-CEO of DC Studios with Peter Safran - added he was feeling this way because "a lot was riding on" 'Superman's success, which would kickstart the DC Universe (DCU) on the silver screen.

While 'Superman' will be a lynchpin for the DCU as the franchise finds its footing, the filmmaker stressed the flick would be a standalone affair.

He explained: "Everything needs to stand by itself. I don't want somebody to have to go see this movie and be relying on anything else. Now listen, once we get down the line, that may change a little bit."

Even so, Gunn added "seeds [were] being planted" in 'Superman' for future projects in the DCU - but stressed they were "never going to be the predominant thing" in the flick or other entries in the series.

He explained: "Yes, there's seeds being planted, but that is never going to be the predominant thing in any scene for me.

"It's always about getting to the next scene. What's in the moment? How are we making this movie the best we can be? And it's going to stay like that as much as I can possibly make it like that."

'Superman' will follow the Man of Steel as he tries to balance his human life and relationship with Lois Lane (Rachel Brosnahan) with that of his responsibilities of being the world's greatest protector, all while his arch-nemesis Lex Luthor (Nicholas Hoult) plans his downfall.

The 'Creature Commandos' producer explained 'Superman' would "start in the middle of the action", with the hero already having been established in Metropolis.

Gunn said: "Superman already exists. Lois and Clark already know each other. Lex hates Superman's guts from the beginning, although they don't know each other personally.

"So, we start right in the middle of the action."

Considering Superman can fly, Gunn took inspiration from aerial sequences in Tom Cruise's 'Top Gun: Maverick' to do justice to the action scenes in his upcoming movie.

The director said: "Being able to shoot stuff in the sky … is really hard. So we took a lot from films like 'Top Gun: Maverick'. We shoot a lot of our action with actual drones flying in and around Superman and the people that he's flying with, The Engineer and whoever else that he's fighting up in the air.

"And we did that on sound stages. We got these really small, crazy drones now. We've got some of the best flyers in the world here who are working with it."

While Gunn had previously said 'Superman' would be a "pretty family-friendly" experience, the filmmaker insisted the flick would be "incredibly grounded" and more serious than his 'Guardian of the Galaxy' trilogy and 'The Suicide Squad'.

He teased: "I start with a place that's very hopeful, fun … but incredibly grounded [and] incredibly serious all at the same time.

"It's humorous, but it certainly is not as [funny] as either 'Suicide Squad' or 'Guardians'."