Iron Ingot

Iron ingots are versatile metal ingots used extensively in crafting.

Smelting
Smelting iron ore is the most common way to obtain iron ingots.

Iron golems
Iron golems drop 3-5 iron ingots upon death, regardless of the way they die. The looting enchantment does not increase the amount of iron ingots dropped.

Zombies
Zombies, husks, and zombie villagers have a 2.5% chance of dropping either an iron ingot, carrot, or potato when killed by a player or tamed wolf. This is increased by 1% per level of looting. This gives iron ingots the following chances of dropping:
 * $1/120$ (about 0.83%)
 * $11/600$ (about 1.83%) with Looting I
 * $17/600$ (about 2.83%) with Looting II
 * $23/600$ (about 3.83%) with Looting III

Trading
Apprentice-level Armorer, Toolsmith, and Weaponsmith villagers buy 4 iron ingots for an emerald as their third trade.

Apprentice-level Armorer villagers have a 50% chance to buy 4 iron ingots for one emerald, and apprentice-level Toolsmith and Weaponsmith villagers will always buy 4 iron ingots for one emerald.

Armorer, toolsmith, and weaponsmith villagers buy 7-9 iron ingots for one emerald as part of their second tier trades.

Repairing
Items which can be repaired with iron ingots in an anvil;

Beacons
Iron ingots can be used to select powers from a beacon. The player must select one of the available powers, and then insert an ingot in the item slot.

An iron ingot can be substituted for an emerald, a gold ingot, or a diamond.

Trivia

 * The iron ingot is the most versatile item in the game, being used in 34 crafting recipes. The second most versatile item is planks with 29 recipes.

Železný ingot Eisenbarren Lingote de hierro Lingot de fer Vasrúd Lingotto di ferro 鉄インゴット 철괴 IJzerstaaf Sztabka żelaza Barra de Ferro Железный слиток Залізний зливок 铁锭