Shane, Rick must be a chemist. Your answer sums up what Rick said in a Nutshe... I mean KitKat wrapper.
The reaction producing rust, most simply put, is:
4Fe + 3O2 -> 2Fe2O3
or more correctly, results from the balanced series of reactions:
4Fe + 3O2 + 6H2O ...-> 4Fe(OH)3
4Fe(OH)3 ................-> 4FeO(OH) + 4H2O
4FeO(OH) .............. -> 2Fe2O3 + 2H2O
If you look closely, the 4Fe(OH)3 and the 4FeO(OH) on each side "cancel" leaving you with the more simple equation equation I wrote above. But, the reaction cannot proceed without the presence of water because it is required in the intermediate steps.
As Rick stated, the metal with the LOWER electrical potential will give up its electrons easier. When Fe becomes Fe2O3 (rust), it has gone from Fe with no charge to Fe3+ because it lost 3 electrons overall. When iron (Fe) gives up its electrons in water according to the process above, that is rusting.
Just so you know, to understand the process completely, you need a grade 12 Chemistry course, and the electrochemistry unit is one of the hardest units in the course.
Tomorrow I will go over how to use the half-cell potentials to put together oxidation/reduction reactions in electrochemical cells, followed by electrolysis.
Hybrid Mode
