Why are metal oxides generally more stable than their corresponding elemental forms?
The oxidation of gold is not favorable.  For many other metals the metallic bonding is weaker than the bonding with oxygen.  

Let's look at the steps in oxidation:

Breaking metallic bonds (endothermic).

Ionizing the metal atoms (endothermic).

Electron affinity of oxygen (exo for the first, endo for the second).

Lattice energy of the oxide (exothermic).

The lattice energy is so high that the process is favorable.