Dressed all in black, pop idol Madonna broke into her hit "Nothing Really Matters" Saturday night before throngs of joyful fans jammed onto Brazil's famed Copacabana beach in Rio.

Shortly after 10:30 pm (0130 GMT Sunday), the 65-year-old singer walked down an elevated bridge from the Copacabana Palace hotel to a massive stage for one of the most important shows of her career.

It marked the final stop on her "Celebration Tour" noting her 40 years atop pop charts, in a free event expected to draw upward of 1.5 million fans from across Brazil.

US electronic dance music master DJ Diplo opened the show as thousands jostled to get a view of the stage. Huge screens dotted the venue. Offshore, boats bobbed in the water, letting those onboard enjoy the show.

"I'm a mess, I haven't slept well, I've been listening to Madonna all week," 29-year-old sociologist Ina Odara told AFP. Tattooed on her shoulder is a phrase from the pop idol: "All that you ever learned, try to forget."

"Madonna helped me leave the Catholic Church, think about many things and change my relationship with my family," said Odara, a trans woman, standing near the huge stage -- twice the size of any used previously on the tour.

Hours before the show, fans were already dancing to Madonna's songs blasting from the speakers on stage.

Police patrolled almost every corner to minimize the usual mass robberies.

- A 'virgin' and a 'material girl' -

After 80 performances across Europe and North America, the Rio concert provided a crowning touch to a tour that took on sudden urgency when the singer in June suffered a life-threatening bacterial infection.

Since the 1984 release of "Like a Virgin," Madonna has released an album every two or three years.

Her shows, with their spectacular productions, set a high bar. But the ever-provocative Madonna has also provided unforgettable moments, like when she kissed Britney Spears at 2003's MTV Music Video Awards.

Her irreverence led to a tumultuous relationship with the Catholic Church, with  Pope John Paul II urging fans to boycott her over her provocative 1989 video "Like a Prayer," seen as blasphemous.

In Rio, the singer was expected to, over a span of two hours, portray all the Madonnas: the "Material Girl," the bride, the rebellious Catholic, the virgin, the cowgirl, and others.

- 'Oi, Rio!' -

The concert should provide an economic boost to Rio, which contributed 20 million reales ($4 million) toward the $12 million cost of the production.

Authorities say the concert should pump a far larger sum -- 293 million reales, or $57 million -- into the local economy.

On every corner in the Copacabana neighborhood are billboards, souvenirs or T-shirts bearing images of Madonna or of the conical corset designed by Jean Paul Gaultier and made famous by the diva.

Since the singer's arrival in Rio on Monday, hundreds of her fans have swarmed outside the Copacabana Palace.

The excitement spiked Thursday night when Madonna unexpectedly appeared for a sound check, her face almost completely hidden behind a colorful balaclava.

That scene was repeated on Friday.

"Oi, Rio!" she called out in Portuguese to fans.

The response on Saturday night from more than a million voices: "Oi, Queen Madonna!"