SAN FRANCISCO — Despite the many legendary hard rock acts with a connection with the City by the Bay, it’s not a typical tour stop on the hard rock and metal circuit. So it’s not hyperbole to say Saturday night’s mega concert with System of a Down and Deftones was the most significant rock show— at least one without locals Metallica—to come here in a long, long time.

The bill, which also featured The Mars Volta, Viagra Boys and VOWWS, felt like an event. Organizers Another Planet Entertainment said the show sold all tickets—more than 50,000—as soon as they went on sale, with about 80 percent of attendees traveling in from outside the area.

The first-ever “Golden Gate Park Concerts at the Polo Field” was also a rare chance to see System of a Down live. The band has played only two other shows in the past two years, both headlining its own Sick New World festival in Las Vegas. The quartet took the stage without the fanfare of dramatic production, picked up instruments and got to work. Opening with “Genocidal Humanoidz,” the band launched into as epic a set as the Golden Gate Park polo field has ever seen.

“From Los Angeles, CA, by way of Armenia, we are System of a Down, and this is System-of-a-Down-style rock and roll,” guitarist Daron Malakian announced.

Vocalist Serj Tankian was stoic and measured, but powerful in his unflinching delivery. Malakian was an enigmatic spark plug, churning out metallic riffs and melodic solos. Bassist Shavo Odadjian was the heartbeat providing the foundation of the sound while drummer John Dolmayan’s thunderous hits drove the sound.

The band brought the heavy material early with “Suite-Pee,” “Prison Song” and rarity “Mr. Jack.” The upbeat “B.Y.O.B.” was the first to really get the majority of the crowd involved with the expertly crafted anti-war song packaged with infectious pop melodies. The Armenian American band’s political astuteness also felt like a callback to San Francisco’s Summer of Love activism. System of a Down didn’t fill its set with political material, but the social awareness in the lyrics added a layer of relevance.

“Stop letting them divide you, your neighbor is not your enemy. The government is,” Malakian said before the band played “Hypnotize.”

It wasn’t all serious, however. SOAD was all smiles throughout the set and looked to be enjoying the unique gig.

“Sometimes we sing sweet songs like [‘Hypnotize’], but we also sing sweet songs about pulling tapeworms out of your eyes,” Malakian before “Needles.”

The band played quite a bit of material off its seminal Toxicity album, spreading the rest of the set fairly evenly between its other records. Lasers shot from the stage and massive banks of spotlights shape-shifted around through the set as System of a Down worked through “Bounce,” “Suggestions” and another rarity in “P.L.U.C.K.” Tankian and Malakian expertly play off each other vocally, with pitch-perfect harmonies that rose and fell with the tension and aggression of the music.

Naturally, “Chop Suey!” was a memorable singalong. The collective explosion of energy from the crowd was something to experience.

Malakian took on more of the vocals on “Lonely Day” and “Lost in Hollywood” as the band worked its way through a barrage of hits. Fiery melodic rocker “Aerials” that might have gotten the biggest reaction of the night.

“How are you feeling San Francisco? You look fucking beautiful from here,” Tankian said late in the show.

SOAD finished out with a double shot of “Toxicity” and “Sugar.” The concert certainly didn’t feel like just another gig under. All smiles, the band hugged at the middle of the stage as the crowd cheered on. This show won’t soon be forgotten.

Not to be lost in the mix, Sacramento’s Deftones gave the crowd every their money’s worth. Vocalist Chino Moreno was the catalyst for their performance, attacking the stage. It was a relatively rare Northern California appearance. The band had a massive contingent of fans in Golden Gate Park, based on the T-shirts in the crowd.

Deftones’ opening was immediate and unrelenting, starting with the melodic power of “Be Quiet and Drive (Far Away)” into the raw ferocity of “My Own Summer (Shove It),” the latter in particular an explosion of energy.

“It’s really wonderful to be here,” said Moreno, who frequently checked in on fans and thanked them.

Songs like “Diamond Eyes,” “Digital Bath,” and “Needles and Pens” hit with precision and the band looked locked in. As with SOAD, Moreno was all smiles and in good spirits. Despite the 50,000 people looking on, the band’s performance felt like a reunion of old friends jamming together.

Moreno’s textured vocals were magnificent and his range dynamic. The singer could whisper intricate and intimate verses before switching into a howling scream. “Rosemary” and “Rocket Skies” hit with power as the band’s patented low-end guitar rumble reverberated down the polo field. Moreno strapped on a guitar for the anthemic “Change (In the House of Flies),” before closing with “Genesis” and “7 Words.”

The trio of opening bands took on decidedly different sounds and performances. The Mars Volta brought a distinctly more progressive aesthetic to the stage, veering closer into jam band territory. The band worked its way through six songs over 45 minutes, many of them included sections of jams, solos and interludes.

Vocalist Cedric Bixler-Zavala was a compelling presence with impressive range. The band also mixed in elements of punk, Latin, classical and hard rock. The intricacy of the music was impressive as was guitarist and co-founder Omar Rodriqugez-López. Playing tracks like “Roulette,” “Drunkship” and “Graveyard,” The Mars Volta brought an entirely different vibe from the other acts.

Swedish punk rockers Viagra Boys leaned deep into their satirical side for a fun and lively performance. The band has a Bay Area connection. Vocalist Sebastian Murphy lived in San Rafael before moving to Europe. He was also full of memorable puns.

“We’re the Deftones, thanks for coming out!” the tattooed vocalist said. “I grew up in the Bay Area, 415 for life!”

Musically, Viagra Boys were a little bit of everything, from hardcore and punk to even new wave. They were the only band with a saxophonist on Saturday.

“We went to the Olympics for Sweden as Viagra Boys,” Murphy announced. “We’re bronze medalists three years running.” The singer had an unusual presence, in sweats and shirtless, but an entertaining one.

“Shout out to the shrimp in the mosh pit,” he said before the band played “Troglodyte.”

Guitarist Linus Hilborg had a unique style that involved using his lighter as a slide on his guitar.

Highlights included “Punk Rock Loser.”

Dark and moody pop act VOWWS kicked off the day, rattling and rumbling through its set.

Follow editor Chloe Catajan at Instagram.com/riannachloe. Follow writer Mike DeWald at Twitter.com/mike_dewald.