De molde literally translates to 'from a mold', but it is used as a colorful expression to describe something that is cookie-cutter, predictable, or lacking originality.
In this empowering track, Beyoncé sings "Los chicos son de molde" to express frustration that boys often act exactly the same way when it comes to taking relationships for granted. It is a fantastic Spanish idiom to learn if you want to playfully call out someone for being totally unoriginal!
Beyoncé takes on a whole new point of view in "Si Yo Fuera Un Chico", the official Spanish version of her R&B hit "If I Were a Boy". She imagines what life looks like from the other side of a relationship, starting with total freedom: wearing whatever she grabs first ("Yo me vestiría como quiero / Con lo que vea primero y me voy" [I would dress how I want / With whatever I see first and leave]), chasing girls with loyal friends, and lying every single night without a second thought. But this fantasy quickly turns into a pointed critique. She argues that because she knows the pain of being taken for granted, stepping into a man's shoes would teach her how to actually treat a partner right: "Sabría escuchar / Pues conozco el dolor / De perder a quien se quiere porque ignoras lo que tienes" [I would know how to listen / Because I know the pain / Of losing the one you love because you ignore what you have].
Notice how she contrasts men and women directly, claiming men act like they are stamped from a generic cookie-cutter ("Los chicos son de molde" [Boys are from a mold]) while women lead with their feelings ("nosotras somos de corazón" [we are from the heart]). By the end, the hypothetical game ends and reality hits hard. She faces her partner directly, telling him it is too late to apologize because his spot is officially gone ("El lugar que ocupabas tú / Ya no está más" [The place you used to occupy / Is no longer there]). The track flips from a playful 'what-if' scenario into a firm breakup speech, calling him out for failing to listen until it is far too late.