While Metallica made metalheads happy on the other end of Zilker Park, French electronic duo Justice closed out Saturday night at ACL Fest from the Honda stage. Here are four things that made the set memorable.

1. A classic is a classic no matter the genre. Hearing the familiar schoolyard chant of “D.A.N.C.E.” wind its way into the sonic steamroller Gaspard Augé and Xavier de Rosnay were piloting was like Rose seeing the lifeboat in “Titanic” — a familiar old friend in the frenzy. “Genesis,” also off 2007’s “Justice,” was a similar sound for sore ears.

2. ACL’s dance-centric headliners through the years all offered something a little different, whether it was Calvin Harris’ pop charts jukebox or Skrillex’s turbulent dubstep inferno or Disclosure’s tight house hypnosis. Justice gave this year’s crowd gothic disco, cinematic slasher flick chords and straight up funk, like on “Love S.O.S.”

3. The lights. That’s half the show, man. Justice didn’t disappoint on optics: LED strobes, rotating spotlights that looked like needles in an anti-grav freefall, liberal use of silhouette. If you’re not going to activate the brain with lyrics, you gotta give the eyes something to feast on, and this set delivered.

4. Half the fun of an electronic headliner set is people watching in the dark, right? There was head-waggling, people perched precariously on shoulders, trains of people who were barely alive holding hands and plowing their way further into the crush of people, the shirtless dudes going in hard on the outskirts of the dancing mob. If you had to describe ACL Fest to an alien, you’d probably just read that sentence to them.

• MORE ACL: Sofi Tukker’s technicolor treehouse turn-up too big for ACL’s tent