Aguacero literally translates to "downpour" or "heavy rain". It's a much more intense and evocative word than the common word for rain, lluvia.
In the song, Sech uses this word in a beautiful metaphor: "Cuando te conocí me estaba quemando y llegaste en forma de aguacero" (When I met you I was burning, and you arrived in the form of a downpour). He uses this powerful imagery to describe how his love interest came into his life and saved him, like a sudden rain extinguishing a fire.
This song is all about that amazing feeling of being completely won over by someone. Sech and ELENA ROSE trade verses about a love that feels like a happy defeat. The title, "1-0", is a soccer score, and they use it to say their partner has beaten them in the game of love. They sing, "Tú me cambiaste / Uno a cero me ganaste" (You changed me / You beat me one to zero). It's not a sad loss, though; it's about surrendering to how incredible the other person is.
They fill the song with sweet and playful details about their relationship. They love how their partner talks, especially "cuando hablas de mí" (when you talk about me), and how they dance, especially "cuando es pa' mí" (when it's for me). The connection is so strong that what started as a "partido amistoso" (a friendly match) has become the real thing. They even compare their bond to a famous piece of technology, saying they are "blindado' como el Cybertruck" (armored like the Cybertruck), protected from anyone who might be jealous.