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By Brooke Sopelsa and Tim Stelloh

Music legend George Michael, known for hit songs such as “Faith,” “Freedom ‘90” and holiday favorite “Last Christmas,” died at age 53 on Christmas Day, reportedly of heart failure.

But the legacy of the pop icon, who sold well over 100 million albums in the span of his career, extends far beyond his music.

"George was probably the first gay pop star in the modern era, who was totally unabashed about gay sexuality,” Martin Aston, a music journalist and author of “Breaking Down the Walls of Heartache: How Music Came Out,” told NBC Out.

Related: Tributes Pour in After Singer George Michael Dies at 53

Even though Michael was forced out of the closet, once he was out, Aston noted, "he took a great leap forward" and "came out guns blazing."

Infamous Outing

Michael's moment of liberation followed what seemed at first to be a time of deep humiliation.

He was blessed with sensual good looks and an exquisite voice, attributes he used to become first a teenybopper heartthrob and then a mature solo artist with videos that played up his considerable appeal. He kept his own sexual orientation private, until he was arrested in 1998 for lewd conduct in a public toilet in Los Angeles after being spotted by a male undercover police officer.

In an earlier era, that might have doomed his career. Instead of retreating, however, Michael made a single and video — "Outside" — that ridiculed the charges against him and mocked the Los Angeles police officers who busted him.

The memorable image of the two uniformed policemen kissing in the video — both funny and outrageous at the time — helped Michael come out as a proud gay man.

LGBTQ Legacy

Despite his infamous outing, “he never dealt with [his sexuality] in terms of shame,” Aston told NBC Out. “He realized he had to be true to himself, and that had to have helped bust that closet door open.”

George Michael performs on stage, Australia, March 1988.Michael Putland / Getty Images

Aston referred to the late pop star as a “very good role model” and credited him with helping pave the way for openly gay contemporary artists such as Adam Lambert and Sam Smith.

Smith, who tweeted Monday for the first time in more than six months, seems to agree: “I would not be the artist I am if it wasn't for you. @GeorgeMichael."

In a separate tweet, the Grammy Award-winning Smith referred to Michael as “one of the most magical, talented, bravest & important figures in music & life as I know it.”

Lambert also took to Twitter to remember the singer, writing simply “RIP @GeorgeMichael.”

While Michael was far from the first musician to come out as openly gay, his status as a mainstream pop icon and his “huge female fan base” made him unique, according to Aston.

“For somebody of that ilk to not worry about their career or their image and be that open about it, was incredibly positive,” he said.

“From the time he was out, there was no sense of shame,” Aston reiterated, adding "the regret was that he hadn’t done it sooner.”

George Michael performs on his Symphonica Tour at The LG Arena on September 16, 2012 in Birmingham, England.Dave J Hogan / Getty Images

Following Michael's passing, a long list of celebrities paid tribute to the music legend, but openly gay entertainer George Takei may have said it best in a comment posted to Twitter on Christmas night:

"Rest with the glittering stars, George Michael. You've found your Freedom, your Faith. It was your Last Christmas, and we shall miss you."

Charitable Giving

Michael was also a prolific philanthropist and supporter of causes that ranged from grappling with HIV/AIDS to protecting vulnerable children. In 2006, he even gave a free concert to the nurses who had cared for his mother. “Society calls what you do a vocation, and that means you don’t get paid properly,” he told the audience of 2,000, according to the BBC. "I salute you."

The pursuit began in 1984, his biography notes, when he performed with Band Aid, the musical charity that included everyone from Bono to Boy George. The proceeds of Band Aid’s chart-topping single, “Do They Know It’s Christmas?" went to Ethiopian famine relief.

Seven years later, Michael donated the proceeds from his acclaimed duet with Elton John, "Don’t Let the Sun Go Down on Me," to the HIV advocacy organization Terrence Higgins Trust, among other groups. His support, the Trust said in a statement Monday, continued for years.

"His donations contributed to a vision of a world where people living with HIV live healthy lives free from prejudice and discrimination," the statement said. "Thanks to George's legacy, we are a step closer to that world and we are so grateful for his support and friendship over the years."

Michael was often quiet in his giving. In a post on Twitter, the English game show host Richard Osman recalled Monday that after a woman on "Deal Or No Deal" said that she needed 15,000 British pounds for in vitro fertilization, Michael "secretly" called the following day and provided the money.

Another Twitter user said that Michael worked anonymously at the homeless shelter where she volunteered.

"I’ve never told anyone, he asked we didn’t," the user wrote. "That’s who he was."

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Associated Press contributed.