What do the chemical reactions that occur during burning and rusting have in common

Rusting refers to a chemical reaction when a metal, in the majority of the cases, iron, reacts with water vapor and oxygen to get transformed into a metal oxide, like iron oxide. Burning is also a chemical reaction, which involves a fuel and oxygen. It discharged high amount of energy in the form of heat.  

Both burning and rusting are examples of oxidation reactions and exhibits oxygen as the oxidizing agent.  

if you're asking what comes out, it's steam.