Iron is a basic resource that is required in order to upgrade most buildings and to craft various battle items.  It is acquired as a reward for successful completion of any stage on the mapWanted Missionstitan battles, and raids, along with it being generated by the watchtower and each mine in your base.
Iron Icon

Sources of Food

The primary source of iron is mines and the watchtower.  Iron is generated at a specific rate per hour (detailed on each building's page).  Each upgrade will increases the amount generated.  While mines are the primary source of iron, the watchtower, with enough outposts under your command, can provide the equivalent of up to 2 mines worth of iron and should not be neglected as a valuable iron source.

Completing stages on the world map also proves to be a significant source of iron.  Stages in later provinces award more iron than in earlier provinces.

There is also a quest that awards a great deal of iron, appropriately called "Mine Iron".

Iron Storage

The building, Iron Storage, increases the amount of iron that one may hold in reserve.  Tapping the iron icon will show one's current maximum.  Upgrading the Iron Storage building increases maximum possible reserves.

Spending Iron

There are currently only two uses for iron in Empires & Puzzles:

  1.  Upgrading buildings
  2.  Crafting battle items in the Forge.

While food is a resource that one can never have too much of, iron is so integral to the base building process that once done upgrading all of the buildings, one generally has an extreme excess of iron.

Most Commonly Crafted Items

Referencing this poll, taken in December, 2018, the five most commonly used items in titan battles that require iron are:

  1.  Arrow Attack
  2.  Tornado
  3.  Axe Attack
  4.  Turtle Banner
  5.  Time Stop
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