Fulmine literally translates to "lightning bolt". It's a striking and evocative word that isn't commonly found in everyday Italian songs.
In the context of the song, the artist uses "Sei stata un fulmine mandato dagli Dei" (You were a lightning bolt sent by the Gods) to describe a person who entered his life suddenly and powerfully, leaving a profound and unforgettable impact, much like a divine intervention. This metaphorical use makes it a captivating and memorable word.
"Rimani Qui" ("Stay Here") is a plea from someone who knows he has made mistakes and is asking his partner not to leave over them.
The chorus repeats the title line again and again: stay here, even if you don't know what to say, even when you doubt me and watch me while you laugh instead of trusting me. He admits he has let her down before, that he gave everything to someone who didn't deserve it, and that he still keeps her clothes in the closet even though she is gone.
In the verses he owns his part in it: he used to hide behind a smile while feeling sad inside, he let arguments and old habits get in the way, and he is only now learning to slow down and stop repeating the same excuses. He asks her to believe that wanting her back isn't just a habit, it's something he genuinely needs.
By the end the song settles into the same repeated plea, as if saying it enough times might be what finally convinces her to stay.