Resplandecen means 'to shine brightly' or 'to gleam'. It's a beautiful, poetic verb that goes beyond the more common word for 'shine' (brillar).
In the song, the artist sings about his lover's eyes, "Con sus ojitos que resplandecen al parpadear" (With her little eyes that gleam when she blinks). He uses this powerful word to capture the magical, radiant quality of her gaze, making it an incredibly romantic and memorable description.
Dominican artist EmmaKings lays all his cards on the table in Ella, a reggaeton track about being completely hypnotized by a woman who holds all the cards. He calls her a mix of good and bad, admitting she has los trucos necesarios (the necessary tricks) to take total control over him. When she whispers "Siénteme" ("Feel me") in his ear, his skin literally gets goosebumps (sólo el roce eriza mi piel). He even calls her his "mami chula", a classic Latin American slang term of endearment that translates to something like "gorgeous girl" or "hot mama."
What makes this track fun is how dramatic his devotion gets. He is ready to trade his entire heart for a single kiss, saying he wants to tie himself to her como un nudo (like a knot). In his eyes, her sparkling blink stands out in any crowd, driving him crazy enough to shout that she is literal tú eres mi todo ("literally my everything").