with an amazing transformation for the upcoming movie "dallas buyers club." matthew McConaughey shed nearly 50 pounds for his starring role in the movie. But jared leto went through a change, losing... See More
with an amazing transformation for the upcoming movie "dallas buyers club." matthew McConaughey shed nearly 50 pounds for his starring role in the movie. But jared leto went through a change, losing more than 30 pounds and changing his look. Abc's nick watt has the story. ♪ Lost in the city of angels ♪ Reporter: Here are a few of the many faces of jared leto. Teenage heartthrob in "my so-called life." And "chapter 27." On stage as the front man of 30 seconds to mars. And now, talking about his first movie role, in six years. So, why did you do it? I did it because I fell in love. I fell in love with the role. Reporter: And the role was rayon. Do you like this dress? Reporter: You're a beautiful transsexual. Thank you very much. Reporter: This is how leto normally looks. This as rayon. Leto lost nearly one-third of his body weight. And waxed everything in sight. I was playing someone addicted to drugs and diagnose of aids. Reporter: Alongside an EMACIATED matthew McConaughey, who contracted hiv in '86 and teams up with rayon in importing and distributing antiviral medication. You stayed in character as rayon, the whole time? It was pretty hard to leave that role. Reporter: Who is he these days? Pretty much full-time musicians. With three critically acclaimed albums and touring the world, with 30 seconds to mars. It wasn't supposed to be successful. But it did become that. Reporter: Acting and the movies is now the sideline. Why are you so good to me? I don't know how long it's going to be until I make another one. Reporter: Nothing else in the pipeline? No. Not at all. Reporter: He'll be back. From this movie, he'll take away a hat full of awards and some life lessons. I learned a lot. It was a beautiful person to get to know. She had this charm and humor and grace and openness. And you hope -- I hope to keep some of those qualities with me. ♪ One life one love ♪ ♪ in the city of angels ♪ Reporter: For "good morning america," nick watt, abc news, los angeles.
This transcript has been automatically generated and may not be 100% accurate.