In the first step of formation of rust in iron, there is something that pulls electrons from the iron lattice, resulting in the formation of $\ce{Fe^{2+}}$. The reaction is:
$\ce{Fe -> Fe^{2+} + 2e-}$
After that positive iron is repelled from the lattice, it is dissolved into water and a lot of reactions take place.
What is the thing that pulls the electrons from iron? (I guess it must be something positive, right?)