Lo mismo literally means "the same thing". However, in this song's powerful chorus, it's part of the essential Spanish idiom "me da lo mismo", which translates to "I don't care" or "it's all the same to me".
This phrase is a bold declaration of self-acceptance and defiance. The artist proclaims that he is who he is ("soy así"), and what others think of him simply doesn't matter, perfectly capturing the song's rebellious spirit.
This song is a fantastic anthem for anyone who has ever felt like they don't quite fit in. Gims kicks things off by admitting he's a bit of a puzzle, a "pêle-mêle, un mélange" (a jumble, a mix). He refuses to be put into the "petites cases" (little boxes) that society creates for people. He knows he's complicated and has no interest in choosing just one side or one path.
Then Alvaro Soler jumps in with that super catchy chorus, "Sí, soy así, me da lo mismo" (Yes, I'm like this, I don't care). It's a powerful declaration of self-acceptance. He questions how he's supposed to fit into someone else's mold when they've already decided the shape and color. The whole song is about breaking free from expectations, learning to fly, and choosing your own desires over other people's opinions, because as Gims says, "La vie, c'est des envies, l'envie avant les avis" (Life is about desires, desire before opinions).