Agradecerte means "to thank you." While "gracias" is common, this verb form is more active and personal, directly expressing the act of gratitude.
In the song, the singer repeatedly expresses deep thanks to their loved one for bringing happiness and healing into their life. It highlights the profound appreciation and impact the person has had, making it a central theme of the lyrics.
La Energia Nortena's "Los Ángeles Existen" is such a sweet song about finding true happiness and overcoming past sadness thanks to a new love. The singer can't believe his luck, asking, "¿Cómo no voy a estar feliz?" [How could I not be happy?] and "¿Cómo no agradecerte?" [How could I not thank you?]. He feels like his heart was falling apart from love until this person stopped him, making him realize that "los ángeles existen" [angels exist].
It's clear this person has brought so much good into his life! He sings, "Con tu amor, ya no me da ni un segundo la tristeza" [With your love, sadness doesn't touch me for even a second]. His past doesn't bother him anymore because their kisses helped him move on. He's got a permanent smile and knows where he's going, guided by the "luz de tu mirada" [light of your gaze]. For him, this person is everything, and he can't help but thank God for their presence.