The single most important piece for weightlifting is the weightlifting bar. Stainless steel is often used, especially for higher quality bars in competitions where they are checked for their durability, bending resistance, and flexibility under heavy loading.
A standard Olympic bar can accommodate anywhere from 20kg to over 450kg. It is therefore important to use a material with a high tensile strength (the maximum stress a material can withstand without breaking) in order to ensure that the bar does not break when lifting substantial weights. The grade of stainless steel used for the weightlifting bar has an extremely high tensile strength of 1500 MPa - making stainless steel the best bar-none for professional weightlifting.