In general, iron isn't used for anything anymore, steel is generally used in places where iron was used in the 19th century.
Steel also rusts to varying degrees except in cases where alloys are used.
Stainless is very good steel, but also more expensive, and harder to work with, as well as being more brittle and amazingly hard. The main element in stainless that makes it resistant to rust is chrome, often derived from chromium and often one of the toxic elements in steel mill tailings. Most metallurgy is somewhat toxic, depending where in the refining process you pick up the raw material, and usually very energy intensive, whether it be through the use of coke furnaces, or electrical furnaces. Even jewelers are often poisoned by the alloys that they make in small quantities.