The metal some glasses are made of is bendy, once bent it recovers on its own, like a spring reguaurdles of how much it is bent. This metal is called metal with memory.

 

If a car was made of metal with memory then during a car crash the car would crumple and stop the passengers and the drivers getting injured. Then it would auto-recover during the next coupple of seconds, just like the glasses?

I don't think this would work for a number of reasons.

 

1/ the memory alloys do not possess enough strength to be used in vehicles. it would be impractical.

 

2/ it could potentially work for minor dents and damage but in a full on crash it wouldn't work where the metal can split.

 

3/ they would need to be heated to 500*C for them to regain shape (yeah i know the frames for glasses can do this quicker but they are smaller and thinner and generally are not subjected to the conditions of a car so can be made of a different alloy) which would fry the interior of the car. and since not all components would be made of the alloy some of these would need to be replaced and taken out before reforming.