Eriza comes from the verb erizar, which literally means "to make something stand on end," like hair or fur. The common phrase is erizar la piel, which is the perfect Spanish equivalent for "to give someone goosebumps."
In "El Malo," the singer contrasts himself with a more boring, "good guy" rival. He claims the girl will always choose him because he's the one "que te eriza la piel" (who gives you goosebumps), describing a raw, electrifying attraction that the safe choice just can't inspire.
Ever been stuck between a good guy and the one you really want? Aventura's "El Malo" is all about that dilemma, told from the point of view of the "bad guy" himself. He knows his ex is with a new man who is sincere and loving, but he's also sure she's miserable, telling her, Él te da su amor, tú duermes con dudas (He gives you his love, you sleep with doubts). The singer is incredibly confident, comparing their situation to a twisted fairytale where she is Cinderella and her new boyfriend is el tonto que da pena (the fool who is pitiful). The singer admits he's no príncipe azul (prince charming), but he is her true love and her biggest problem.
He's not humble about it at all. He claims the new guy doesn't even know Cuando y como darte un beso (when and how to kiss you), while he knows all her secrets. The song's core idea is that being a nice, faithful person isn't always enough to win someone's heart. As he puts it, No basta los morales, y ser fiel / Si tú deliras por el malo que te eriza la piel (Morals and being faithful are not enough / If you go crazy for the bad guy who gives you goosebumps). It's a classic bachata story about a love that's passionate and maybe a little toxic, but impossible to forget.