Elastic and plastic materials
Elastic materials can be deformed by exerting a force on them but they return to their original shape when the force stops.
The rubber in rubber bands is an elastic material.
By contrast, plastic materials stay in their new shape even after the force ceases. Plastic materials are a category of materials and should not be confused with the material "plastic" (e.g. plastic bags).
Porcelain is a plastic material. A force strong enough to deform porcelain would cause it to stay in its deformed state (i.e. break).
No material is infinitely elastic. If an elastic material is stretched beyond the elastic limit, it will be permanently deformed.
A steel spring, for example, is elastic up to a certain degree. Stretching it too much will leave it permanently stretched or even ruptured.