You can get seed from a head of cabbage if you grow it yourself. It is a biennial vegetable so it will grow the head the first year and if you leave it in the ground over the winter it will sprout seed heads the next year. You can buy seeds to plant or you can also find seedlings to transplant at garden centers.
Copper and bronze do not contain any iron, and only iron can rust (because rust is defined as iron oxide, a compound of iron and oxygen); so the answer is that steel will rust the fastest and copper and bronze will never 'rust'. But, yes, copper and bronze do tarnish, they do corrode.
Rust is the process of metal oxidation. It is a chemical burning undergone by iron. Rust can happen when metals are in contact with water, air, oxygen, or acids. The main catalyst of metal rust is water, because its molecule can penetrate pits in any exposed iron. When metals are exposed to the corrosion-causing agents for quite long time, some of the parts will turn into orange-colored powder, known as rust. This substance has long been blamed for some health disturbances.