Metta World Peace was born Ronald william Artest Jr. on November 13, 1979, and raised in the Queensbridge projects in Queens, New York. He has two younger brothers, Isaiah and Daniel. He played high school basketball at La Salle Academy. He also teamed with Future NBA players Elton Brand and Lamar Odom on the same Amateur Athletic Union (AAU) team.

In the late 1990s, World Peace became a close friend of American-born Irish basketball legend, Jermaine Turner. The pair met on the playgrounds of New York, and played together in tournaments at Rucker Park.

Growing up, Artest witnessed the murder of a fellow player on a basketball court in Niagara Falls, New York. "It was so competitive, they broke a leg from a table and they threw it, it went right through his heart and he died right on the court. So I'm accustomed to playing basketball really rough." The player to whom Artest was referring was 19-year-old Lloyd Newton, who was stabbed in the back with a broken-off table leg during an altercation at a 1991 YMCA-sanctioned basketball tournament.

Artest played college basketball at St. John's University from 1997 to 1999. At St. John's, he majored in mathematics. In 1999, he led the Red Storm to a 14-4 record in the Big East Conference and 28-9 overall and the Elite Eight of the NCAA Division I Tournament, losing to Ohio State.

Artest played a total of 175 games for the Bulls over 2-1/2 years, the bulk as a starter, during which time he averaged about 12.5 points and just over 4 rebounds per game. He was named to the NBA All-Rookie Second Team in the 1999–2000 season.

Midway through the 2001–02 season, Artest was traded by Chicago to the Indiana Pacers along with Ron Mercer, Brad Miller, and Kevin Ollie, in exchange for Jalen Rose, Travis Best, Norman Richardson, and a 2nd round draft pick.

World Peace and Kimsha Artest (née Hatfield) were married for 6 years. Kimsha was a cast member on VH1's reality TV show Basketball Wives: LA. The two have three children together: Sadie, Ron III, and Diamond. Kimsha and World Peace, who was still named Ron Artest at the time, married in June 2003 and divorced in 2009. World Peace has another son, Jeron, with his former high school girlfriend Jennifer Palma.

On November 19, 2004, Artest was at the center of an altercation among players and fans during a game in Auburn Hills, Michigan between Artest's Pacers and the home team Detroit Pistons.

After the playoffs, Artest offered to donate his entire salary to keep teammate Bonzi Wells with the team, who became a free agent after the 2005–06 NBA season. He even jokingly threatened to kill Wells if he did not re-sign with the Kings. Wells was later picked up by the Houston Rockets and then traded to the New Orleans Hornets for former Sacramento Kings player Bobby Jackson. Artest also offered to donate his salary to retain the services of head coach Rick Adelman, whose contract expired after the same season. Adelman and the Kings did not agree on a contract extension so the two parted ways.

On October 31, 2006, Artest released a rap album entitled My World. He published the album on the Lightyear Records label under his own imprint, Tru Warier Records. The album features guest artists P. Diddy, Juvenile, Mike Jones, Big Kap, Nature and Capone.

On March 5, 2007, Artest was arrested for domestic violence, and excused from the Sacramento Kings indefinitely by GM Geoff Petrie. On March 10, Kings announced that Artest would return to the team, while his case was being reviewed by the Placer County District Attorney. On May 3, he was sentenced to 20 days in jail and community Service. Artest spent only 10 days in the jail, as the judge stayed 10 days of the sentence, and served the remainder in a work release program. On July 14, 2007, the NBA suspended Artest for seven games at the beginning of the 2007–08 NBA season for his legal problems.

On October 30, 2008, Artest received his first technical as a Houston Rocket, as he raced towards a group of Dallas Mavericks players and then quickly went to Yao Ming who bumped Josh Howard after play stopped. Artest was trying to pull Yao away from the play and to the foul line, but contact was made with Maverick players. The TNT broadcast crew felt this technical was not warranted, and was based upon Artest's prior reputation as a feisty player in the league. In the playoffs, Artest helped the Rockets advance past the first round for the first time in 12 seasons. In Game 2 of the second round against the Los Angeles Lakers, Artest, who was battling for rebounding position with Kobe Bryant, was elbowed in the neck by Bryant, which was later ruled to be a Type 1 flagrant foul. After being called for an offensive foul, Artest was indignant and proceeded to antagonize Bryant after the play, which eventually led to an ejection by Joe Crawford. In Game 3, Artest was again ejected in the fourth quarter after a hard foul on Pau Gasol, who was attempting to dunk on a fast-break. It was determined the next day that the foul was not serious enough to warrant an ejection, and the flagrant foul was downgraded.

During his rookie season in Chicago, he was criticized for applying for a job at Circuit City in order to get an employee discount. In a December 2009 Sporting News interview, Artest admitted that he had led a "wild" lifestyle as a young player, and that he drank Hennessy cognac in the locker room at halftime while with the Bulls. In February 2004, he wore a bathrobe over his practice uniform to a Pacers practice as "a symbolic reminder to take it easy".

He has become involved in advocacy relating to mental health issues. In December 2010, he announced that he would donate some or all of his salary for the 2011–12 NBA season toward mental health awareness charities. Artest also auctioned off his 2009–10 championship ring and donated the proceeds to various mental health charities nationwide. In 2016, he told Sports Illustrated, "Some people don’t understand mental health is broad. You have to ask questions. Are you depressed? Are you schizophrenic? Do you have anxiety? Are you bipolar? Those are the different things that come under the banner of mental health."

On September 16, 2011, Artest's name was officially changed to Metta World Peace. "Metta" is his first name, and "World Peace" is his surname. "Changing my name was meant to inspire and bring youth together all around the world", World Peace said in a statement released after the name change court hearing. His publicist, Courtney Barnes, said that World Peace chose Metta as his first name because it is a traditional Buddhist word that means loving kindness and friendliness towards all.

In October 2012, he guest starred as a special panelist on Nickelodeon's game show Figure It Out.

The brawl began when Artest fouled Pistons center Ben Wallace as Wallace was putting up a shot. Wallace, upset at being fouled hard when the game was effectively over (the Pacers led 97–82 with less than 50 seconds to go), responded by shoving Artest, leading to an altercation near the scorer's table. Artest walked to the sideline and lay down on the scorer's table. Reacting to Wallace throwing something at Artest, Pistons fan John Green threw a cup of Diet Coke at Artest, hitting him. Artest jumped into the front-row seats and confronted a man he incorrectly believed to be responsible, which in turn erupted into a brawl between Pistons fans and several of the Pacers. Artest returned to the basketball court, and punched Pistons fan A.J. Shackleford, who was apparently taunting Artest verbally. This fight resulted in the game being stopped with less than a minute remaining. Artest's teammates Jermaine O'Neal and Stephen Jackson were suspended indefinitely the day after the game, along with Wallace.

On August 4, 2014, World Peace signed with the Sichuan Blue Whales of the Chinese Basketball Association. Due to a recurrent knee injury, he was replaced on the roster in December 2014 with Daniel Orton. In 15 games, World Peace averaged 19 points, 6 rebounds and 2.3 steals per game.

On September 24, 2015, World Peace signed with the Los Angeles Lakers, returning to the franchise for a second stint. On November 6, 2015, he made his season debut in a 104–98 win over the Brooklyn Nets, playing 17 minutes with a plus-minus of 12. Teammate Kobe Bryant praised him for his impact on "everybody on the floor defensively".

On September 21, 2016, World Peace re-signed with the Lakers. On April 11, 2017, World Peace scored a team-leading 18 points in the second half to help the Lakers extend its longest winning streak in four years to five games with a 108–96 victory over the New Orleans Pelicans. He had the ball in his hands with the crowd on its feet for the Lakers' final possession in what was potentially his final game at Staples Center. During the game, he got his 1,716th and 1,717th career steals to move past Ron Harper for 22nd place in NBA history. During the offseason, World Peace played with the New Orleans Gators of the Global Mixed Gender Basketball (GMGB) League.

On October 23, 2017, World Peace was hired as a player development coach by the South Bay Lakers, the Los Angeles Lakers' development-league team in the NBA G League.

In January 2018, it was announced that World Peace was a contestant in the first U.S. edition of Celebrity Big Brother. Metta became the fourth Celebrity to be evicted from the house on Day 20.