There are many uses for iron in Minecraft. It is arguably the most sought after resource. While diamonds are the best, iron is a better choice. Iron has more benefits and is easier to find. Iron is most commonly used to make armor and tools, but iron doors are another useful use.
Iron doors are awesome because they can't be clicked open and mobs won't break them down. This is how to make and use them in Minecraft.
Iron ingots are used to make iron doors. They can be obtained by melting raw iron (or ironore if it is version 1.16 or older) at a one percent ratio. Three of the six ingots used for iron doors will be made. They will still need more iron to work.
Iron pressure plates can be used to help with iron doors. A pressure plate is required to activate the door. However, only heavy pressure plates will work. Three pressure plates can be made from two ingots. Redstone pulses are required to open iron doors.
Redstone devices such as levers and buttons will open the doors, but they must be within one block of it. The Redstone will emit redstone, so the levers will keep the doors open. However, everything else will make the door close.
In terms of placement, iron doors are the same as wooden doors. They must be placed in a 2-block opening.
Iron doors, unlike wooden doors that can be broken by mobs on Hard difficulty, are invulnerable to anyone but a player. Iron doors are not allowed to be used by villagers or other mobs unless they accidentally step on the pressure plate, or are shown how.