Messi has been known to sometimes let go of singing the anthem on multiple occasions and there have been instances when he has sung it too, but for the most part of it, Messi stays silent next to his teammates during the whole procession.
The Barcelona legend was once asked about this and he handed out a straightforward reply that his devotion and love for Argentina goes beyond the act of singing the anthem before international games and that he choose to express his love for his country in a different manner.
"I get annoyed by the people who attack you without thinking. I won't sing the national anthem on purpose. I don't need to sing it to feel it," he told TyCSports in 2015.
Messi added, "It reaches me, every person feels it in their own way. The Pumas cry, they feel it differently and that's ok. I play with the national team always as a priority and I want to win everything I play."
While he doesn't sing the anthem on the field, a young Argentinean mascot has revealed that Messi hums the national anthem before kick-off.
Tomas Chavez got to meet Messi during Argentina's fixture against Qatar in 2019.
"He caressed me and his hand was bigger than my head, that's why he laughed," Chavez told Marca.
He added, "I hugged him and told him a lot of things: that I loved him, that he is my idol, that I always wanted to meet him and never had the opportunity [to do so]. [During the anthem] he has his mouth shut and hums the anthem. It's true that he does not sing the hymn, but he hums it. I heard it."
Argentina national anthem lyrics (abbreviated 1924 modern version)
Oid, mortales, el grito sagrado:"¡Libertad! ¡Libertad! ¡Libertad!"Oíd el ruido de rotas cadenasved en trono a la noble igualdad
Ya su trono dignísimo abrieronlas Provincias Unidas del Sudy los libres del mundo responden:"¡Al gran pueblo argentino, salud!"Y los libres del mundo responden:"¡Al gran pueblo argentino, salud!"
Sean eternos los laureles,que supimos conseguir.Coronados de gloria vivamos¡O juremos con gloria morir!¡O juremos con gloria morir!
Hear, mortals, the sacred cry: "Freedom! Freedom! Freedom!" Hear the sound of broken chains See noble equality enthroned. Their most worthy throne have now opened The United Provinces of the South. And the free people of the world reply: "To the great Argentine people, hail!" And the free people of the world reply: "To the great Argentine people, hail!" May the laurels be eternal that we were able to achieve. Let us live crowned in glory Or let us swear to die with glory! Or let us swear to die with glory!