Donning a black, velvet, strapless gown, the former Gossip Girl star completed her classy look with leather boots, long gloves and plenty of jewels around her neck.
“A transformation -- what do you think I normally look like?” Lively said after ET commented on her glam red carpet transformation. “It is. I don't look like this.”
Lively explained that she had starkly contrasting looks in TheRhythm Section and finds it amusing when people guess which one is closer to her real-life sans makeup look.
“I was in a ton of makeup in order to have these eye bags and look as rough as she looks in the beginning and then I was also in a ton of makeup [for] when she looked nice and fresh,” she shared of her character’s look in the movie. “The real me is somewhere in the middle.”
“Some people see it like, ‘This is what she looks like without makeup,’ and it's the horrible one and then sometimes [it’s like,] ‘This is what she looks like without makeup,’ and it's the fresh-faced one -- that also took an hour," she added. “So, it's funny to see different people's perspectives of how good or how awful I look without makeup.”
Lively stars alongside Jude Law in the thriller, portraying a spy name Stephanie Patrick, who’s on a mission to find out the truth about a plane crash which killed her family.
“This movie is grounded in humanity which you don't normally see in this genre,” said the actress, who took her mom, Elaine, and sister, Robyn, to the screening. “It's people beating people up and shooting guns and getting into car chases and there's no examinations of what that must actually be like to come face-to-face with another human life.”
“There are no real good guys or bad guys -- everybody's doing what they believe in,” she continued. “Everyone's just fighting to survive in these extreme circumstances and she's not a trained operative. She's not an assassin. She's a girl who had nothing left to lose and decides she's going to fight back and she's probably going to die trying, but she's going to try.”
Lively also filled ET in on the accident she was involved in which shut down the film’s production in 2017. She suffered a hand injury from the incident, but admitted she was too stubborn to head to the hospital right away.
“That day was not my favorite day,” she said. “I'm not sure if it's the take that's in the movie because I did shoot till the end. I'm the person who doesn't ask for directions and I have a real ego about all that stuff. I was like. ‘It's fine, my hand’s fine!’ After a few days when my hand just looked like Jello, I thought, ‘You know, it's time to go to the hospital.”
The Rhythm Section hits theaters Jan. 31, and ET went behind-the-scenes with Lively on the film. Check out the video below.