In physics, elasticity refers to a material's ability to deform under stress and return to its original shape when the stress is removed. A material is considered more elastic if it requires a greater amount of stress to produce a given amount of strain (deformation). This property is quantified by the elastic modulus (e.g., Young's Modulus). Steel has a significantly higher Young's modulus compared to copper, rubber, or sponge, meaning it is much stiffer and resists deformation more effectively within its elastic limit. While rubber can undergo large deformations and return to its shape, steel requires much greater force to deform even slightly within its elastic range.