Solea'o is a colloquial, shortened form of "soleado," which means "sunny." It's a common way to speak in many Spanish-speaking regions, especially in informal contexts like song lyrics.
In the song, Myke Towers repeatedly uses "el día está solea'o" (the day is sunny) to set a relaxed, positive, and inviting mood. It suggests a perfect day to spend with a loved one, reinforcing the romantic and intimate themes of the lyrics.
"SOLEAO" is Myke Towers and Quevedo's ode to shutting the world out and staying wrapped up with someone for a sunny day. Most of the song plays out indoors, away from cameras and the people trying to figure out what is really going on between them. The mood is playful and unhurried: a couple of shots, a movie left half-watched, and two people happy to keep to themselves.
Underneath the flirting there is some honesty too. The singer admits his past has caused problems and that love has put him through hard times, but he asks his partner to trust him anyway. The song circles back to a beach memory that sparked the connection, and closes on a shrug about keeping things low-key rather than official, "only in quotation marks."