A steel rod is bent by applying force to two or more points on the rod in opposition. The amount of force necessary and how the steel bends depend on several factors including strength and toughness.
There is no one kind of steel. As stated by SteelConstruction.info, steel is rated by five different categories. The first is strength, or the ability for the steel to keep its shape. The second is toughness, or the ability of the steel to bend rather than break or shatter when it is put under stress. The third is ductility, or the ability of the steel to be pushed together or pulled apart without cracking or failing. The fourth and fifth qualities, weldability and durability, do not impact how steel bends.
A steel rod with low strength and high toughness bends quite readily. A steel rod with high strength and low toughness resists being bent, but shatters and breaks off instead of bending when it does give way.
Steel is an alloy of metals combined under specific conditions. A steel's composition, smelting, forging and tempering affect all of the five characteristics mentioned. Characteristics for any given piece of steel are generally available from the manufacturing company.