Cowboy (and rain) boots were the attire du jour for Boston Calling on Friday, as the wettest day of the fest collided with its country-heavy billing.

The first night also brought faithful Fenway vibes as fans joined a “Sweet Caroline” singalong during a rain-soaked intermission while waiting for headliner Combs to perform. The short delay before his set proved to be worth the wait, as the country star charged up the Green Stage and “didn’t let up for an hour and a half,” according to Globe reviewer Marc Hirsh.

The “When It Rains It Pours” singer’s set featured a cameo by fellow country star Megan Moroney, who performed earlier in the night on the Green Stage. She rocked a personalized Red Sox jersey while joining Combs for a rendition of his song “Beer Never Broke My Heart.” Combs noted in an Instagram post that Moroney had been an extra in the song’s music video and asked her to jump in on Friday night when he saw they “were playing the same festival.”

Other highlights from the day included Sheryl Crow, rewarding fans who weathered the late-afternoon rain with crowd-pleasing hits like “Soak Up The Sun.” She offered a small bit of political commentary too, at one point shouting out, “I don’t know, Bruce Springsteen for president?” while wearing a T-shirt featuring the rocker.

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Meanwhile, singer-songwriter Max McNown played up to the New England crowd by performing the Noah Kahan’s “Stick Season,” calling the Vermont crooner, “one of my greatest inspirations.” Over on the Blue Stage, rapper T-Pain showed off his dance moves and kept the party going with nostalgic bangers like “Buy You A Drank (Shawty Snappin’)” and “All I Do Is Win.”

Boston band Dalton & the Sheriffs served as a last-minute replacement for TLC. The R&B group dropped out “due to an unexpected medical circumstance,” the fest announced early Friday afternoon.

Read Globe correspondent Marc Hirsh’s day one review here and check out more photos from Friday below.

Saturday’s lineup was a trip down memory lane for millennial pop-punk fans, culminating with headliners Fall Out Boy. From hits like “Thnks fr th Mmrs” to newer tracks like “So Much (for) Stardust,” the band surveyed its lengthy discography, with plenty of pyrotechnics thrown into the mix.

Fans who caught Fall Out Boy’s set were treated to another “Sweet Caroline” moment, as singer Patrick Stump broke out the Neil Diamond tune during a brief piano interlude. The band also teased the opening to the Dropkick Murphy’s “I’m Shipping Up to Boston” before diving into “Bang The Doldrums.”

Avril Lavigne also brought the pyrotechnics and a heavy dose of pink pop punk aesthetics to the Green Stage with her early 2000s angsty teen anthems like “Sk8er Boi.” Lavigne later brought singer Alex Gaskarth from All Time Low out to perform their recent track “Fake As Hell.” (All Time Low performed earlier in the day on the Green Stage as well.)

The Maine, Black Crowes, Cage the Elephant, and James Bay were also among Saturday’s lineup of performers.

Read Globe correspondent Victoria Wasylak’s day two review here and check out more photos from Saturday below.

The final day of the fest brought the best weather, along with a mix of poignant tributes and political moments on stage.

Headliner Dave Matthews Band wound back the clock to the ’90s as the group played hits like “Tripping Billies.” During the set, singer Dave Matthews shared a message of hope for fans who felt like “the world has lost her mind” while calling out “mis-leaders.” After the performance, Matthews returned to the stage holding up a pair of signs that read “Stop killing children” and “Stop the genocide,” which he has brought out at previous events.

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On the Blue Stage, former Rage Against the Machine star and Harvard alum Tom Morello was back in his old stomping grounds. During his set, Morello reminisced with the crowd about his days in Cambridge. He also welcomed them to show with a heavy dig at the Trump administration, saying, “the last big event before they throw us all in jail.” (His stage and guitar were adorned with anti-Trump and -ICE motifs.) Morello also shouted out the Springsteen-Trump feud, adding: “Bruce draws a bigger audience,” before playing the Springsteen classic “The Ghost of Tom Joad.”

Morello also paid tribute to former Audioslave bandmate Chris Cornell with a rendition of “Like a Stone,” calling it “more of a prayer than a song” while honoring the late singer. The tributes continued on the Blue Stage with Public Enemy’s Flavor Flav and Chuck D, as the duo got the crowd to shout well wishes for recovering Celtics star Jayson Tatum. Flav also paid tribute to “Cheers” actor George Wendt, who died last week, telling the audience, “we gotta pour one out for Norm.” Chuck D and Morello teamed up for a song during the evening as well.

Other highlights from day three included Sublime, with singer Jakob Nowell honoring his late dad and the band’s former singer Bradley Nowell, as Sunday marked 29 years since his death. Amid a cloudy overcast, he added: “If you’ve got a family member or loved one who isn’t here with you tonight, I just want to let you know that they are here, man, sure as that [expletive] sun’s going to come out again.” The sun ended up breaking through the clouds shortly afterwards as the band performed, with Nowell later joking, “Yeah, we planned it.”

Vampire Weekend, Remi Wolf, Spin Doctors, and more also performed on Sunday.

Check out more photos from Sunday below.

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Globe correspondents Haley Clough and Marianna Orozco contributed to this report.

Matt Juul can be reached at matthew.juul@globe.com.