Question: 
What types of chemical reaction are able to form water?

Answer:
Lots of them!

• The synthesis reaction of hydrogen with oxygen results in the exothermic formation of water.
• The decomposition reaction of carbonic acid (H₂CO₃) results in the formation of water.
• The single displacement reaction of hydrogen with iron (II) hydroxide forms water, though it requires a lot of energy to make it happen.
• Any combustion reaction forms water (as well as carbon dioxide and lots of heat).
• Just about the only type of reaction that doesn't form water is a double displacement reaction.  Double displacement reactions that form water are better known as acid-base reactions.