Various possible defences against drones have been put forward; may I add my twopence worth?
In my infosec days, there was concern expressed about the ability of "HERF" (High Energy Radio Frequency) guns to damage electronic equipment in data centres. Now, I know such things have been built using magnetrons such as those from microwave ovens; but I'm unsure whether anything exists that could fry a drone's electronics at a range of (say) 150 metres or so. Attacking the drone's electronics directly would make it unnecessary for the drone to be under direct control to be vulnerable - also avoiding the problem of flying metal.
FWIW Wikipedia has an article on "directed energy weapons".