Mark Ruffalo isn't always angry, but when he is, he's usually sporting a certain shade of green, and standing with Earth's Mightiest Heroes.

Ruffalo makes his Marvel once again in next summer's The Avengers: Age of Ultron. Right now, however, he's at the Sundance Film Festival with his new movie Infinitely Polar Bear, in which he plays a man with bipolar disorder. Speaking with Total Film, Ruffalo said he hopes to continue making movies with powerful messages, and that he wants to bring that attitude to his studio projects — including those at Marvel.

"As artists we have an ability to reach a lot of people in a deep way, and we have a responsibility," he said. "What we have to do as storytellers is to take science and make it relatable. I think we have to tell the story of the positive and what we're going to try to do. Give them alternatives but don't make it a polemic."

"I'm in The Avengers, but if you took my screen time it would come to about 10 minutes, along with the 12 other people I'm sharing the screen with, so my input's kind of limited on that," he added. "But if we get to a standalone Hulk movie, I'll have a much better chance to do that. I'm just learning now how to find my voice and bring it into the studio world."

Although the Hulk's appearance in 2012's The Avengers received "a phenomenal response" from audiences," the last we heard, Marvel has no plans for a solo film. However, as Ruffalo said last year, "One never knows what the future will bring.”

His next announced appearance as the Jade Giant occurs in The Avengers: Age of Ultron, hitting theaters on May 1, 2015.