"It's a fantastic movie. So ambitious. So romantic and sweeping," says Weaver, who was shooting again this week. "I can't wait to get back."
Weaver has only positive things to say about her co-star, Macbeth star Worthington.
"He's a terrific actor, he really is. And a lovely guy. I think he's going to do a wonderful job. His humor and charm and just genuineness as a person are very evident as soon as you start working with him."
Weaver says she plays a botanist who mentors Worthington's character.
"I'm not allowed to give too much away, but we have parallel adventures. There's a younger person's story and a smaller, older person's story all happening at the same time. All my scenes are with [Worthington]. It's really a lovely relationship."
Avatar opens May 22nd, 2009.