It didn’t take much for Harry Melling to sign onto “Pillion.” The 36-year-old actor had, somewhat by chance, seen writer and director Harry Lighton’s short film “Wren Boys” and thought it was “exquisite,” so when the script arrived from his agents, Melling was immediately on board. 

It was, however, a bit of a different story when he told his friends and family about the film. 

“A lot of them were quite shocked when I mentioned the scenes of orgies in the woods and alleyway blow jobs,” Melling says, the morning after the film’s New York premiere. “But once you read the whole thing, all that stuff makes sense in the context of what the movie’s doing. I just knew immediately that I was game.”

“Pillion,” which is Lighton’s first feature film, premiered last year at the Cannes Film Festival and finally arrives in U.S. theaters Friday. The movie follows Colin, a quiet, timid man who lives with his parents, works as a parking ticket attendant and sings in a choir, whose world is turned upside down when he meets a leather-clad biker named Ray (Alexander Skarsgard). Colin enters into a BDSM relationship with Ray, and soon finds himself in a group of dom-sub gay leather bikers, with a shaved head and a new wardrobe to match.

“First off, I loved his bravery and I loved his curiosity,” Melling says of Colin. “I love characters that are complicated, and Colin is really complicated in lots of ways. We meet him, and he hasn’t quite happened yet. He hasn’t found his footing in life. He’s not tortured, which was important for me and Harry Lighton to be very clear with that. He’s not tortured in any way — the only person that’s holding him back is himself. And you meet him at the point where he wants something to happen, and then he goes on this wild journey meeting Ray and exploring who he is and what love means to him and what sex means to him.

“I love the journey from inexperience to experience, and watching this person follow his instincts, and maybe not at all times knowing what he’s got himself in for, but knowing that somewhere at the end of this road is something worthwhile. All these things were just golden to act with because it was a really nuanced, complicated script, and yet on the surface of it, it was very accessible, and I really was excited to have a go at doing that.”

Early in the film, Colin leaves his family on Christmas night to go meet Ray for the first time, and the two have a rather explicit encounter in an alley. Melling has watched “Pillion” now five times, and the alley scene remains his favorite to experience with an audience.

“It is really very much the moment in the movie where it sort of surprises the audience. It takes an interesting turn, because up to that point, it’s kind of quite warm and fuzzy,” he says. “It’s a sort of Christmas family movie, and then Colin goes down the alleyway following Ray and the audience go, ‘oh wow, no, OK, here we go. We’re into something else now.’ And I always love watching an audience realize that. And in a way, I think that’s the reason why I said ‘yes’ to the movie in the first place, was those two things sort of rubbing alongside each other, for lack of a better phrase. The sort of very warm and familiar alongside the unfamiliar.”

Ahead of filming, Lighton reached out to the GBMCC, or the Gay Bikers Motorcycle Club, for Melling’s research. Several of the members ended up making it into the film, as part of Ray’s group.

“I started hanging out with them, and they were just the most incredible, lovely, generous, amazing people that I’ve ever met, just gorgeous,” Melling says. “And then Harry said, ‘I’m thinking of putting the GBMCC members, alongside some members of the London kink scene, into the movie.’ And I was like, ‘that’s just the best idea.’”

Through his time with the members he learned both how to ride a motorcycle as well as how to lick a boot, for a particular scene with Ray. The encounters with the bikers left him “moved” by their generosity. 

“It is a very exposing thing and vulnerable to talk about, that part of your life, which is very intimate. I was really moved, and I’m so grateful that they really sort of trusted us, and felt that we were going to take care of their stories and their lives,” Melling says.

Melling first broke out for his role as Dudley Dursley in the Harry Potter films, a far cry from the world of BDSM. 

“All that happened when I was so young, and I always knew I wanted so much from this career. I always wanted to act, and I wanted to have as rich and as varied a career as possible. And so I think I took certain steps, not necessarily to maneuver from ‘Harry Potter,’ but just to try and get better,” Melling says. “So I did drama school and did lots of theater for many, many years, and that was just building an understanding of how I wanted to act. I don’t really feel that it kind of pigeonholed me at all because it was so young when I did it. But the thing that I was always chasing was ‘how do I try and have the most interesting career that I’ve always dreamed of doing?’”

Ahead, Melling will star opposite Jodie Comer in a musical horror film called “Stuffed,” and is committed to finding new ways to surprise himself.

“I love that feeling of going, ‘oh, yes, this is something that I really feel that I can offer something to.’ Even if it’s completely wrong, I love that feeling,” he says. “The idea of climbing the ladder, all of that stuff is very abstract to me as a thing. I’m far more interested in going, ‘ah, this moment here is something that I feel excited by, and I want to explore that.’”