Formiga means "ant". It's an interesting word choice because it's a common insect, but its use in this song is quite poetic and metaphorical.
Lulu Santos sings, "Assim caminha a humanidade / Com passos de formiga / E sem vontade" (Thus humanity walks / With ant steps / And without will). He uses the image of an ant's small, slow steps to describe humanity's progress as gradual and perhaps even reluctant, making a simple word carry a deeper, philosophical meaning.
This song is a really honest look at the slow process of healing after a relationship ends. Lulu Santos sings about how it takes time, saying "Ainda vai levar um tempo pra fechar o que feriu por dentro" [It will still take some time to close what wounded inside]. It's a natural process, for both people involved, and it's not something that happens overnight. He even mentions it will be a while "pra gente poder dar risada" [for us to be able to laugh] again.
My favorite part is when he describes how humanity moves forward: "Assim caminha a humanidade com passos de formiga e sem vontade" [Thus humanity walks with ant steps and without will]. It's such a blunt and relatable way to talk about how slow and sometimes unwilling progress can be, especially when you're dealing with emotional recovery. He's clear that he doesn't wish the other person ill, but also very firm: "Apenas não te quero mais" [I just don't want you anymore]. It's a simple, direct message about moving on, even if it's at an ant's pace.