Mercurio means "Mercury," but in this song, it's not just about the planet. KAROL G is referencing the popular astrological concept of "Mercury in retrograde," which is often blamed for communication breakdowns and arguments.
She sings, "No le eches la culpa a Mercurio" (Don't blame it on Mercury), telling her partner that their relationship problems aren't caused by the stars. It's a very modern and clever way to talk about a lover's quarrel, making it a unique word to find in a pop song.
In "MERCURIO," Colombian star KAROL G is in the middle of a fight with her partner, and she's not holding back. She lays out her rules for love: when two people fight, they don't ignore each other. Instead, they should be talking, kissing, and sending texts "hablando de sexo" [talking about sex]. She's tired of excuses, especially blaming relationship problems on astrology. She sings, "No le eches la culpa a Mercurio" [Don't blame Mercury], telling him their issues are about them, not the planets.
She's trying to make up, mixing sweet and spicy lines to get her point across. One moment she's saying "este corazoncito es sólo tuyo" [this little heart is only yours], and the next she's complaining that not texting him goodnight "se siente una mierda" [feels like shit]. She's clear that love shouldn't be about pride or suffering. It's a direct, honest plea to stop fighting and get back to the good stuff.