Paul McCartney and Jennifer Hudson were among the stars playing supporting roles at gun-reform rallies.
Both have a personal connection to gun violence.
Hudson, who performed "The Times They Are A Changin'" to cap Saturday's event in Washington, D.C., alluded to the shooting deaths of her mother, brother and 7-year-old nephew in 2008.
McCartney said his decision to join the New York City march was prompted by the 1980 Manhattan killing of John Lennon, his former Beatles bandmate.
Hundreds of thousands of teenagers and supporters rallied in the nation's capital and other U.S. cities to call for gun control, headed by survivors of the school shooting in Parkland, Florida, that left 17 dead.
McCartney said his decision to take part in the New York City rally was prompted by the 1980 Manhattan shooting death of John Lennon, his former Beatles bandmate.
“One of my best friends was killed in gun violence, right ’round here, so it’s important to me,” he told CNN.
Asked what he hoped could be accomplished by the event, McCartney opened his jacket to show the slogan emblazoned on his black T-shirt: “We can end gun violence.”
Hudson, appearing tearful as she concluded her appearance, was backed by members of a Washington choir and survivors of the Feb. 14 Parkland, Florida, high school shooting. Students from the school led rallies attended by hundreds of thousands of people in the nation’s capital and other U.S. cities.
Celebrities attending the Washington event included power couples George and Amal Clooney and Kate Capshaw and Steven Spielberg, who helped fund the protests with a combined $1 million donation. Also attending were Kim Kardashian and Kanye West, Glenn Close, Cher, Jimmy Fallon and Dennis Rodman.
Common, Cyrus, Andra Day, Vic Mensa, Demi Lovato, Lin-Manuel Miranda, Ben Platt and Ariana Grande performed in Washington, and Rita Ora took the stage in Los Angeles.
“This song is dedicated to Stephon Clark, Decynthia Clements and all the unarmed black men and women killed by police weapons,” Mensa said before performing “Now We Could Be Free.”
Grande encountered another iteration of violence when her 2017 Manchester, England, concert was bombed, killing 22 people and injuring scores of others.
Schumer, the actress-comedian and cousin of Senate Minority Leader Chuck Schumer, a New York Democrat, spoke to Parkland survivors attending the Los Angeles rally, telling them the violence they endured has to stop.
Wearing a #MSDStrong sweatshirt Miley Cyrus performed 'The Climb.'
Andra Day and Common performed 'Rise Up'
Lin-Manuel Miranda and Ben Platt delivered an emotion rendition of "Found/Tonight," a mash-up of songs from Hamilton and Dear Evan Hansen.
Vic fittingly performed his song "Now We Could Be Free."
Demi Lovato perfomed 'Skyscraper.'
Ariana Grande wearing a "March for Or Lives" sweatshirt performed 'Be Alright.'
Jennifer Hudson, who lost her mother, brother, and nephew to gun violence, took the audience to church with her soulful performance of 'The Times Thy are A-Changin.'