Galones literally translates to "gallons", but in a military or hierarchical context, it refers to the "stripes" or "insignia of rank" worn by a captain or officer.
In this song, it's used metaphorically to represent the captain's achievements, leadership, and the respect he has earned. The line "caminamos tus galones y yo" (your stripes and I walk) beautifully conveys the idea of honoring and following the captain's legacy and leadership, making it a unique and evocative word choice.
A football song that never leaves the pitch. The verses stack one phrase on top of the next — "Toda la vida peleando y luchando para ser titulando" (A lifetime fighting and struggling to make the starting eleven), "Toda la vida sacando de banda yendo a rematar" (A lifetime taking throw-ins, going up to shoot) — so the captain's career arrives as a list of small repeated jobs rather than a highlight reel. The number is specific: "Con el nueve a la espalda grabado" (With the nine on your back). So is the low point, "Que nos bajó de primera a segunda con tanto dolor" (That took us down from the first division to the second, with so much pain), and what the captain did with it: "La convertiste en un juego valiente de pulso y amor" (You turned it into a brave game of nerve and love).
The chorus is the stand talking back. "Lleva al equipo al final, que tu puedes" (Take the team to the final, you can do it) is an instruction; "No dejes nunca de estar y ser cómo eres" (Never stop being here, and being who you are) is closer to a plea. Dani Martín ends on the line the whole song exists for — "Que sepas y te sientas, capitán" (So that you know it, and feel it, captain) — and sings it twice, because the point is that the man being sung to should hear it.