The actor, who plays Quicksilver, is currently working on the follow-up to 2016’s relatively ill-received X-Men: Apocalypse.
That itself was a continuation of the soft reboot started by X-Men: First Class in 2011, and X-Men: Days of Future Past in 2014.
Dark Phoenix is essentially the beginning of a new trilogy, and is set ten years after Apocalypse.
“I think it’s the classic X-Men: First Class tone, where there’s a bit of humour thrown in there, but it’s much darker than the previous one, Apocalypse,” Peters told Collider.
“Apocalypse was the ’80s, so there was a lot of room for goofy stuff in there.
“This one is a much more serious film about the internal struggle of Phoenix and Jean, so it’s a dramatic film.”
He added: “There’s nothing very comedic about it, other than the few moments that are in there. I think it’s gonna be a powerful one.
“It’s Dark Phoenix. I think it’s gonna be darker than we’re used to.
“It’s gonna be a change, but it’s gonna be fun for everybody.”
The entire current roster of X-Men stars appeared briefly in Deadpool 2 in a surprise cameo, with the film coming out last month.
Peters revealed that he didn’t realise what they were filming at the time, because it was shot in the middle of other Dark Phoenix scenes, and Ryan Reynolds was not on set with them.
He said, according to Cinema Blend: “We did a bunch of different versions, some not PG, and they ended up using that one.
“I thought it was going to be for the end credits – and I think everybody kinda did – but it ended up being like, boom, right there sort of in the first half of the film. Which was really sort of weird and shocking.”
X-Men Dark Phoenix is due in February 2019.