For most materials, if they are bent out of shape, they stay that way. However, if a part made from a shape-memory alloy (SMA) is bent out of shape, when it is heated above a certain temperature it will return to its original shape.
This property makes it useful for making spectacle frames - they return to their original shape if they are put in hot water after bending them.
SMAs are used as triggers to start the sprinklers in fire alarm systems, controllers for hot water valves in showers or coffee machines and for spectacle frames.