Its the alarm, just pull the crimp off, it won't harm you or the car, I turned mine round as the front side had gone rusty, haha just span it round but i need a new one.
All cars will be different as all cars will have aftermarket alarms fitted with different people putting things in different places.
Mine i had to move when i changed to facelift headlights and it doesn't quite make contact when the bonnet is shut. Had a spate of the alarm going off on windy days since, but ive still yet to find a new location for it....or an alternative fitting.