Luceros is a poetic word for “stars,” often carrying a more luminous or romantic feeling than the everyday word estrellas. In the song, the narrator travels through the galaxy, conquering the luceros with flowers, creating a vivid and dreamlike image of stars being treated like something beautiful and reachable.
Manuel Medrano turns a trip through space into a sea monster story. The singer is "navegando por toda la galaxia" (sailing through the whole galaxy), "conquistando con flores los luceros" (winning over the stars with flowers) and surfing waves on a beach, all in the same breath. It is dreamy and a little silly, and that is the charm.
Then the twist: "Encerré al mar en la tierra por ser el peor enemigo de la galaxia" (I locked the sea on Earth for being the worst enemy of the galaxy). The ocean is the villain here, and the singer worries what happens if it gets out: "apagaría el sol" (it would put out the sun) and "Todo sería mar, no habría nada más" (everything would be sea, there would be nothing else). A useful phrase to learn is acabar con, as in "Solo el mar podría acabar con todas las galaxias" (only the sea could wipe out all the galaxies). On its own acabar means to finish, but acabar con something means to destroy it. Listen also for the conditional verbs, sería, habría, existiría, estarían, which carry the whole "what if" of the song.