All metallic objects, including bikes, can rust. If you leave a bicycle outside in the elements, other moisture speeds up the rust process. That kind of corrosion can destroy your bike frame, cease up your steering, or stop your gear and chain. It's just like mom and dad said, put your bike away when you're done using it.

What you should do is keep it protected from the elements, in a place like the garage, carport, or shed.