According to People magazine, Styles was featured on the cover of a magazine in which he spoke about making it into the Marvel film as Thanos' brother Eros.
"I'm only in right at the very end. But who didn't grow up wanting to be a superhero, you know? It was a great experience and I'm so grateful to have gotten to work with [director] Chloe [Zhao]," Styles told the publication.
He also spoke about continuing along the acting path in girlfriend Olivia Wilde's upcoming film 'Don't Worry Darling' and in 'My Policeman'.
"I like to challenge myself and do something different and movies are definitely where I feel most out of my comfort zone," he said.
Styles continued, "I'm coming from music where I don't think anyone really knows how it works, but I am somewhat in my comfort zone! But in movies, when I show up, I'm the new guy. I haven't been [an actor] for a long time and that's really cool, I feel like I've learned so much and life is about learning."
In fact, Styles said acting has helped him in his music and revealed, "I think music and acting really aid each other in a lot of ways. In my experience, a lot of the time when I've gone to do a film I've felt like, 'Oh, I'm probably not gonna do any music for a while because I'll be so focused on that.' And then I actually find that, by the time I get home at the end of the day, I just write so much."
"Any time you are looking at the world through someone else's lens and exploring different emotions, it feels like a benefit in so many ways," he added.
'Eternals' director Zhao spoke with Deadline about the movie and her decision to cast the Grammy winner, whom she said she had on her mind for years. "Harry as Eros was very much a package deal for me," Zhao said.
Styles appears in the post-credits scene of the latest Marvel instalment with Pip the Troll, voiced by Patton Oswalt.
Zhao revealed she "pitched the idea" of Pip the Troll and Eros to Marvel Studios president Kevin Feige a while back. "I love the idea of exploring an Eternal who is beyond Titan and who may have influenced Thanos throughout the years the same way Eternals influenced us, earthlings," she said.
The 'Nomadland' director added that the pitch came with Styles, who appeared in Christopher Nolan's 2017 film 'Dunkirk', in mind.