The actress met transgender teen Gavin Grimm during the party on April 25, and shared a photo of the moment.
“I’m grateful to have someone like you @grimmgavin for myself and my children to look up to,” Lively, 29, wrote on Instagram. “If you haven’t read his story, google him. He’s a real life hero who’s using his singular voice to stand for so many. I’m with you @grimmgavin.”
Grimm, who spent most of his high school career fighting to use the boy’s bathroom at his Virginia school, was named to the annual list. He wrote a letter, shared exclusively with PEOPLE, thanking TIME and the transgender rights community for pushing the movement forward.
“It has been an honor to serve as an ambassador, as a representative of a community so vibrant, so resilient, and so loving. I thank that community for their support, and in return I promise to continue telling your stories and affirming that you and I have a right to be here, to exist in public life, and to be happy,” Grimm, 17, wrote.
RELATED VIDEO: Gavin Grimm Says the Battle Over Bathroom Use “Should Never Have Happened”
“We are going to win. The fight might be long, but the victory will be worth the perseverance. I encourage other trans students to not sit on the sidelines. Stand for something, not against something. Stand with someone, not against someone. Stand with me, and I’ll stand with you.”
“Met some magical, innovative, badass people last night. Thank you #Time100 for including me on this list. And any night that ends in a huge, snappy dance number is a good night by me,” Reynolds, 40, wrote.