I had this happen on my '85 4-banger 'Stang. The passenger side strut had managed to somehow tear the metal around the tower, and decided to 'pop up to say hello' one day while driving. It was a good thing the hood was properly attached, as it was the only thing holding the strut mount under the hood!
Mind you, yes, that side of the car was pounded back into shape after a 'small' wreck the previous owner had. It made for fun driving until I could weld it back into place; this was only possible because it was more of a tear than rust or corrosion. Because they use so much salt on the roads here in Michigan, I no longer drive Mustangs from mid-October until the rains wash the roads off in the spring. Small price to pay for keeping the metal intact.