Bengala literally translates to "flare" or "sparkler." It's a visually evocative word that brings to mind bright, fleeting moments.
In the song, it's used metaphorically to describe the intense, passionate, and perhaps ephemeral nature of the relationship between the two protagonists. They "shoot stars into the air like bengala," suggesting a desire to create brilliant, memorable moments together, even if they are temporary.
"Bengala" is Lorenzo Fragola's take on a relationship that keeps flickering between falling apart and holding on. The chorus leans on two striking images: bengala, the handheld flares people light up in stadiums and on beaches, and niagara, standing in for a rush of feeling too big to control. "Piove, nell'aria" (it's raining, in the air) turns the weather into the tension hanging between the two people in the song.
The verses describe stolen kisses in the street and the strange, cold feeling of being apart, and the singer admits that wanting to hate each other is exactly what keeps pushing them apart. Even so, the outro keeps circling back to "io e te" (you and me) staying out late together, as if neither of them is ready to really let go.