FLUSHING MEADOWS, New York — For the first time in three years, fans got to return to Citi Field for Mets Opening Day at full capacity. Their enthusiasm was as big as their numbers — they sold out the ballpark on a day with perfect weather, and high optimism. Some fans mentioned the ongoing pandemic, but didn’t let it eclipse the overall mood of excitement.

The man who goes by the nickname “The Pin Man,” because of the hundreds of Mets pins affixed to his many jerseys, summed up the scene succinctly.

“We’ve got the greatest fans in the world!” he exclaimed, in front of a group of tailgating fans before Friday’s home opener. The Pin Man, whose real name is Nick Giampietro, also emphasized one other point, in case anyone doubted the depth of his devotion to the Mets, or his collection.

“I’ve got thousands of pins at home,” he said.

Thousands of fans were not at home, however. They packed Citi Field to capacity — more than 42,000 attendees were recorded by the team, under a cloudless, Mets blue sky.

Before the game, tailgaters were out in force, making up for lost time. One group of longtime party partiers was pleased to be back together after being apart for so long.

“We were here last year, when they said you couldn’t tailgate, only four of us,” said Tommy Dolan, the unofficial mayor of what’s called “Dolan’s Corner.” It’s a large group of people who assemble around barbecue grills, tables and other al fresco dining and drinking trappings, and they’ve been doing so since the Mets’ home opener at the Polo Grounds in 1962.

Now, 60 years later, said Dolan, they’re back — all 102 of them.

One of the most fascinating fans may be Lucia Fernandez. The Oceanside, Long Island high schooler showed up at Citi Field with her homemade “Welcome Back Mets” sign, which she carried with hands decked out with a manicure in Mets blue and orange, as well as a one fingernail painted like a baseball, and another bearing the uniform number of her favorite Mets player, Pete Alonso.

When asked how strong of a fan she is, Fernandez replied, “On a scale of one to ten, eight or nine, maybe?”

The smile that she gave while responding indicated that the number should be higher. The ligatures, or elastic ties, on the braces on her teeth alternated blue and orange, the Mets colors. She was armed to the teeth with loyalty, literally.

Another longtime fan on hand was Terri Collarean. She’s attended Mets Opening Day since the Polo Grounds days in the early 1960s. She brought her niece, Erin Sprague.

“My first opening day ever,” Sprague said. “I’m so excited!”

She’s a nurse at Mt. Sinai Medical Center. She and her aunt said that they’re fully vaccinated, and that having full attendance at the ballpark, even with the pandemic ongoing, is vital.

“This is going to be our future,” said Sprague, adding that people have to live with COVID. “We can’t sacrifice the things that enhance our lives, and that’s baseball.”

Collerean, her aunt, picked it up from there.

“This is New York. Think of all the challenges New York has faced over the years,” she said. “We’re gonna enjoy [the game.] We’re gonna be safe.

“Look at this day,” Collerean continued, as she pointed up to the cloudless sky, on a lovely spring day. “Look at this gift. And we’re gonna win.”

The Mets beat the Arizona Diamondbacks in their first full-capacity home opener since 2019, 10 to 3.