Amber Heard Was Sold on 'Aquaman' at the Empowering Chance to Wield a 'Sword and a Crown' (Exclusive)

The actress also opened up about the disparity in roles available for male and female actors.

Amber Heard is the first to admit that she never thought she'd be starring in a comic book movie. But when the opportunity arose to play warrior royalty in the upcoming Aquaman film, she was ready to wield her power.

"They had me at sword and a crown," Heard recently told ET's Ash Crossan at the premiere of her latest film, London Fields. "[Executive producer] Zack Snyder and I spoke on the phone and I didn't really think a comic book [film] would be something that would be appropriate for me. I didn't really... knowing nothing about the comic book world, knowing nothing about the universe, I didn't really have any reason to feel like that would resonate with my sensibilities or my core principals."

"I had a limited experience, limited exposure to women in that world and then... he explained this badass, kickass warrior queen to me and I thought, again, sword and a crown? OK!"

In the film directed by James Wan, Heard stars opposite Jason Momoa's titular hero as Mera, the daughter of King Nereus (Dolph Lundgren), who has been groomed her entire life to be the queen of Atlantis. However, her best-laid plans take an unexpected turn when she joins Aquaman in his quest to keep peace between the seven seas and the surface world. For Heard, the opportunity to play a heroic character in her right, rather than a damsel in distress, was the empowering selling point to step outside her comfort zone in the DC Comics story.

"I remember the first scene I read in this comic and Mera and Aquaman... had just saved a town from some aquatic disaster, hurricane, or something of that effect, and as the townspeople or the civilians are picking up pieces of their life they look and they say, 'That's Aquaman!' and they look to Mera and they're like, 'Who are you? Is that Aquawoman?' And she stops what she's doing and she says, 'I'm not Aquawoman. I have my own name. My name is Mera.' and I was like, 'I can get behind that woman!'"

The central conflicts of Aquaman stem heavily from the equilibrium between Arthur Curry's humanity and his superhuman destiny, and for Heard, Mera is an essential part of that balance.

"It's a very special dynamic, and one that does not put the burden of dependency on one or the other," she said of the on-screen relationship between hero and heroine. "I like that as a woman, I'm not relegated into a position of dependency or subservience. I love that she is self-possessed and in control of her own destiny. She's powerful, she's nuanced. She has her own attitudes and her own problems and they counter that of his."

"Specifically speaking to their dynamic, where one is strong, the other is weak and vice versa. They come from two different worlds, quite literally, he comes from land, she comes from Atlantis... and in doing so you create a dynamic that's fair, it's balanced, it's equal. They are both providing for one another that which they didn't [have] before."

As for her future in the DC Cinematic Universe, the actress said she's excited for the opportunity to possibly star alongside Wonder Woman and more female heroes from the comic canon. "There's so much room for all of the badass, kickass, never-before-seen and undiscovered... We're just talking about two superheroes that happen to be women, that means there's so much room for so many more characters," she noted. "There's definitely a demand for it. So we just need to keep yelling for it."

Heard, with 'Wonder Woman' director Patty Jenkins and star Gal Gadot, at San Diego Comic-Con in July. - Albert L. Ortega/Getty Images

"There's a lot of room for shared time. Shared screen. Shared pages with so many versions of kickass females out there. It's about time we have more."

While the actress concedes that she's noticed some behind-the-scenes changes since the push for gender equality in Hollywood gained hashtag-level visibility in recent years, she is unwaveringly passionate about the fact that equal-opportunity screen time is still "severely limited for women."

"We make up over half the population -- over half the ticket purchasing decisions, over half the movie-going population. Yet we're represented in 30 percent of the speaking or named roles? Come on. We make up half the population that are auditioning for these parts and yet we speak one-third of the time? It's ridiculous," Heard scoffed. "We're paid less. We're represented poorly. We are represented a fraction of the amount time and that's just assuming that we are represented at all -- and that's the win and that is not the win."

"I feel lucky to be working, but I will keep fighting tooth and nail for chances to flesh out more opportunities to express various parts of the female experience... We have a long way to go. We have a lot to do."

Heard noted that the struggles women face in the workplace are universal. Actresses, in particular, have a tendency to be pigeonholed and diminished in a way that rarely seems to befall their male counterparts.

"I have been forced into a marketplace where I am in a time constraint that is half that of a man's. I get paid a fraction of his salary for more work in terms of hours and in terms of sweat equity," she explained. "I wish I had more ability to stand in front of you today and say, 'Yeah I have a wide, varied [filmography], my resume is a broad spectrum of different characters.' But that's not really true. I've done the best with what I could in a system that is so behind and so broken and so misogynistic and limited. I am happy to be one of the few women who are pounding their fists against the glass walls and ceilings which we have been kept underneath far too long."

Progress, Heard believes, lies in "changing the way we're having these conversations."

"You're asking me these questions, when four years ago you might not be inclined to ask me in such a way. We care about my answer slightly more and in a different way than we did four, five years ago. So that's where the change is. The result of revolution is like that of protest and demonstrations. It's not meant to be overnight. It's not in policy change. It's in the conversation change, it's in attitude change. We're not going to change any policies or any practices unless we change the attitudes by which we approach these subjects."

See Heard take on her heroic new role in Aquaman, out Dec. 14. London Fields is in theaters now.