Adele made a confession last month in St. Paul: She was “scared” to perform in massive arenas in 2011. So she settled for playing to half the arena even though ticket demand easily could have filled the entire venue, probably twice over.

This month, she had more than enough confidence to sell out the entire Xcel Energy Center twice. She probably could have added two more shows.

But in the busiest summer ever on the Twin Cities music scene, it takes more than confidence to fill an arena, stadium or even a theater. Why do some concerts by such stars as Adele and Justin Bieber do big business and others by the likes of Selena Gomez and Macklemore play to half-empty arenas?

It takes a combination of talent, timing, marketing, music, a connection with fans — and sometimes just a little luck.

How did Metallica’s Aug. 20 date at the new U.S. Bank Stadium become the single hottest music ticket of the year in the United States? Because it’s the only concert that the immensely popular metal kingpins are playing this year. Call that timing and luck. There is a pent-up demand to see one of the most potent hard-rock bands of all time. Because fans know that Metallica will rock you to your core with headbanging volume, soul-purging vocals and thrashing power chords.

That show is a no-brainer. So was Adele — the hottest act on the planet — at the X for two nights, and country superstar Luke Bryan at U.S. Bank Stadium, the very first music event at the Vikings stadium.

Those stars know how to connect with their crowds. Bryan shakes his booty, which is what female fans talk about, and hoists a beer or two, which is why the guys are high-fiving. Adele is a world-class yakker, telling fans everything from what she had for lunch to why she wrote a particular song.

Removing the barrier

Making a connection with the fans is an indelible tattoo that will keep them coming back. After more than three decades of touring, Boy George of Culture Club knows that.

“I always look at the audience. I engage with them. I try to remove that weird barrier that sometimes exists at shows,” said the veteran British singer, who has done the arena circuit but will perform with Culture Club on Sunday at the Myth nightclub in Maplewood. “Generally if you’re warm and friendly with an audience, they will respond. I love it when an artist speaks to me; sometimes it’s my favorite part of any show. I went to see [David] Bowie and when he spoke, it was exciting. That’s how you make an emotional connection with the audience.”

Some stars may reach fans via recordings, the radio, TV appearances, videos, websites or social media, but that doesn’t mean they can connect in concert.

Take pop star Gomez, a widely known celebrity from her days on the Disney Channel in “Wizards of Waverly Place.” Last month in front of 8,000 at Xcel Energy Center, the 23-year-old Instagram goddess looked terrific, boasted a stylish stage but didn’t showcase a memorable voice, presence or command. It takes more than a name and massive Instagram following to become a big-time concert success.

The Zac Brown Band drew about 35,000 to Target Field in May but didn’t deliver big time. It had only one, little-known opening act, and didn’t up the ante from its arena shows. Overall, Brown fell far short of the stadium country-music standards set by Bryan and Kenny Chesney, with multiple big-name opening acts and high-energy performances.

Right time, right place

How does a promoter know when it’s the right time and right place for a certain star?

Research is the key. Promoters check to see an artist’s presence on radio, sales in record stores and online, activity on social media, timing with a new album release and how the act fared last time it performed in the Twin Cities.

“Sometimes [record] labels and agents try to fast-track artists and put them in bigger capacity venues than they should,” said Minneapolis consultant Kyle Heino, who founded Concert Marketing Solutions in 2006. “Promoters like Live Nation and AEG Live take this formula across the country and try to apply it to the top 30 markets, and in isolated markets, it doesn’t work.”

Beyoncé is an example of not all markets being similar. She drew one of the smaller crowds on her current tour to Minneapolis TCF Bank Stadium in May — 37,203 fans — compared with 48,304 in Boston and 46,529 in Seattle. Maybe playing outdoors in Minneapolis before Memorial Day was misguided.

Heino thought it unwise of pop-oriented hip-hop stars Macklemore & Ryan Lewis to perform in Minneapolis a mere 10 days after the hugely popular Soundset hip-hop festival that drew 30,000 at the State Fairgrounds. Macklemore had been part of that festival in the past but he attracted only 5,000 to Target Center last month.

Career building

Timing is everything in the music business, not just when and where to play but at what point in an artist’s career.

Some modern acts such as Bieber and teen singer-songwriter Shawn Mendes went viral, jumping quickly from internet sensations to big-venue attractions. While Bieber leapt directly to sold-out arenas after tons of radio airplay, Mendes moved quickly from 2,700-seat Northrop auditorium last year to 5,500-capacity Roy Wilkins Auditorium next month. Neither paid the traditional dues of starting on the club circuit and building a following and a career.

“An artist that’s suddenly huge and disappears quickly or settles into smaller rooms, where does their career go?” asked Nate Kranz, general manager at First Avenue. “I put more stock in paying dues to have a lasting career.”

It worked for a certain once-shy singer from England.

“Adele paid her dues,” Kranz said.

She played the intimate Theatre de la Jeune Lune in 2008, then the 1,000-seat Fitzgerald Theater the following year, and she was scheduled to play 1,500-capacity First Avenue in 2011 but canceled because of laryngitis. Her makeup date later that year was at the X with a half-arena setup, and everyone knows the rest of the story.