Salir por piernas is a fun Spanish idiom that literally translates to "to leave by legs". Its real meaning is to run away, bolt, or flee from a difficult situation.
In the song, Alvaro Soler describes himself as the kind of guy "que no se sale por piernas"—one who doesn't run for it. He's making a statement that he's loyal and dependable, someone who will stick around through thick and thin, unlike someone who might flee at the first sign of trouble.
Spanish singer Alvaro Soler leans straight into his own simplicity here, pitching himself as the ultimate unpretentious boyfriend. He is not trying to act tough or pretend he fits into a flashy club scene. Instead, he laughs at his own flaws: he has zero tattoos, cannot dance, and rocks a basic playera (t-shirt) while his partner steps out head-to-toe in fancy Chanel. When he sings, "A ti te gusta reggaetón, yo prefiero poesía" ("You like reggaeton, I prefer poetry"), he owns the mismatch completely. Even his driving soundtrack is deliberately retro: he cruises around late at night blasting classic 80s pop icon Phil Collins on an old-school radio cassette player.
What makes the track stick is how he turns being totally ordinary into his biggest charm. He relies on being gentle and loyal, promising he is the guy who opens the door for you, kisses you when you wake up, and will stand by you through thick and thin with "Voy contigo a la guerra" ("I'm going to war with you"). Look out for the fun Spanish idiom "no se sale por piernas" (literally "doesn't leave on legs"), which means he is not the type to get scared and run away. He knows he is clumsy—confessing that he only feels like he dances well after a couple of drinks—yet he promises that being an everyday tipo normal (normal guy) is more than enough to lift someone up to the moon.