In the video, the 22-year-old star talked about the connection between the themes of the film and the mission of To Write Love on Her Arms, an organization dedicated to inspiring hope and finding help for people struggling with depression and addiction.
"To Write Love on Her Arms is something truly special, and there is a lot in common with the mission and this movie," Zac said. "Charlie St. Cloud is a story about overcoming loss and grief, about the power of love to help you discover a life worth living. I know that is a message you care about, too."
In the film, Zac's character, Charlie, loses his younger brother, Sam, in a tragic car accident, and after seeing visions of him in the woods, Charlie struggles to let him go and start over. Watch Zac's message to his fans after the jump. Charlie St. Cloud opens in theaters everywhere on July 30.