“High” is track 2 from Zella Day’s debut album, “Kicker. It was released as the first single original to the record.
When Zella spoke with Billboard, she said this:
"It’s a sad reality amongst lovers, when the need to seek outside substances becomes the source of fulfillment in the relationship."
These outside substances are drugs, which the song condemns as her character over-romanticizes her mutual destruction with a boyfriend.