Locura translates to "madness" or "craziness". It's a powerful and evocative word that goes beyond simple love, suggesting an intense, overwhelming obsession or passion.
In the song, the singer expresses, "Esta locura que siento por ti" (This madness I feel for you). It perfectly captures the extreme, almost irrational, depth of his feelings for someone he can only admire from afar, making it a memorable and enticing word to explore.
The whole song hangs on one wish: "Si yo fuera ladrón" (If I were a thief). And what he would take is listed with zero subtlety. "Me robaría tus besos" (I would steal your kisses), then your caresses, then "Me robaría tu cuerpo" (I would steal your body). It starts sweet and gets bolder line by line, which is half the fun.
The reason for the fantasy is sadder than the chorus lets on. He only gets to look at her from a distance, "Porque tú no me permites / Ni un segundo de tu tiempo" (Because you don't allow me / Not even a second of your time). So the thief idea is his way out of being ignored. My favourite line is "Me metería sin permiso" (I would sneak in without permission), followed by "Dentro de tu pensamiento" (Inside your thoughts). He is not breaking into a house; he wants to break into her head. For a learner, notice "fuera" and "robaría": that pairing of the past subjunctive with the conditional is exactly how Spanish says "if I were, I would".