Like the rigid plastics, they are more strong than tough, and don't deform very much under tensile stress. But when strength is what you need, fibers have plenty of it. They are much stronger than plastics, even the rigid ones, and some polymeric fibers, like Kevlar TM , carbon fiber and ultra-high molecular weight polyethylene have better tensile strength than steel. Elastomers like polyisoprene , polybutadiene and polyisobutylene have completely different mechanical behavior from the other types of materials. Take a look at the pink plot in the graph above.
Elastomers have very low moduli.
You can see this from the very gentle slope of the pink plot, but you probably knew this already. You already knew that it is easy to stretch or bend a piece of rubber. But it takes more than just low modulus to make a polymer an elastomer. Being easily stretched is not much use unless the material can bounce back to its original size and shape once the stress is released. Rubber bands would be useless if they just stretched and didn't bounce back.