Iron

Iron is the External Physical Pulling Metal. An Allomancer burning iron can Pull bits of metal toward their "center of self," and can also use iron to sense the presence of metal nearby. Ironpulling is not dependent on magnetic forces or Allomantic power--most metals (with the exception of aluminum and some of its alloys) can be Pulled. Feruchemists can use iron to store physical mass, and when used as a Hemalurgic spike, iron steals physical strength.
The paired alloy of iron used in the Metallic Arts is steel.
== Allomantic Use ==
An iron Misting is known as a Lurcher. Ironpulling is the art of burning iron to pull metals toward (in a straight line) the user's "center of self," which is likely tied to the Allomancer's Cognitive and Spiritual aspects. There are two general rules for Ironpulling, which also apply to steelpushing, its paired opposite. The first rule is that the strength of your pull is roughly proportional to your physical mass. This means that larger Allomancers can generally Ironpull and Steelpush more powerfully than a smaller counterpart. While proportional, the force exerted by an Ironpull is much greater than the Lurcher's weight, allowing them to pull themselves through the air by pulling on a piece of metal that weighs more than they do (or is anchored to something that does). The second rule is that metal that is at least partially inside a person's body cannot be affected by iron. Both of these rules can be overcome by a sufficiently strong Lurcher, however. 
When burning iron, blue lines emerge from the Lurcher and connect themselves to pieces of nearby metals, with the size of the iron line indicating how big the metal is. The iron lines can typically only be seen by the Lurcher. The iron lines manifest themselves on the Spiritual Realm and can be cut or interfered with. It is also possible to use the iron lines to see via the trace metals in everyone's bodies and in the objects around them, or even Axi and electromagnetic bonds. A Lurcher could identify specific metals, or even colors, with the iron lines.
Of the two external physical metals, iron is by far the less flashy. Utilized by a Misting, iron is generally used as a purely defensive mechanism, cancelling out the efforts of enemy Coinshots by Ironpulling enemy projectiles into a wooden shield. Iron is also less useful by itself in jumping, since using iron requires a large, well-anchored piece of metal at your destination. Both metals' performance are greatly enhanced when used in tandem, allowing feats like those performed by Kelsier in his battle with the Inquisitor Bendal.
Iron Allomancy is strongly resisted by the body of sophonts, thus making metalminds embedded into the body difficult to pull. Due to this, some Feruchemists choose to surgically implant their metalminds into their body. However, a strong enough Ironpull, such as one powered by the Mists, is able to overcome this resistance. The degree of resistance is proportional to how Invested the target is, and would therefore require more force to pull metal in the body of someone such as Susebron and an average Scadrian, who would be harder than a Drab. The same limitations apply to Invested metal.
An especially skilled Allomancer can Pull on individual parts of a metal object. Through unknown means, a Lurcher could Pull on non-metal objects. Due to it being possible with Steelpushes, it is supposedly possible to affect the polarity of Axi via an Ironpull, under the right circumstances. Lurchers can also Pull on liquid metals, which would work similarly to the behavior of ferrofluids.
== Feruchemical Use ==
An iron Ferring is known as a Skimmer. Iron is used to store or retrieve (gain) physical mass. This is accomplished by changing the Skimmer's mass, not by changing the effect of gravity on the Skimmer, i.e. it does not modify weight directly. This change does not affect things that the Skimmer wears, but is great enough that a Skimmer storing mass can typically safely fall any distance, as the Skimmer's surface area is typically sufficient to slow the fall to safe speeds.
A Skimmer tapping iron can grow proportionally heavier than normal, and although this is not as useful as storing mass in many cases, it has significant martial applications. Specifically, by tapping iron during key moments, Skimmers can add force to their blows, and can use added weight to withstand attacks. It can be used to counter Coinshots or Lurchers, for example. By increasing weight when pushed, one can instead push the Coinshot back. Furthermore, the added mass from tapping an ironmind can wreak havoc with Steelpushes and Ironpulls if the Skimmer is being used as the anchor. 
Tapping iron grants the Skimmer the strength required to remain standing, including a partial increase in the density of their body, but this increase in density is limited and does not, for example, affect the Skimmer's vulnerability to penetration. Storing weight costs the Skimmer some strength.
The law of conservation of momentum still exists when using iron Feruchemy, so while tapping weight doesn't significantly increase the speed of falling (not considering air resistance), decreasing one's weight to half will double one's speed.
Feruchemical iron interferes with an individual's interaction with the Higgs field. It also allows people to easily adapt to low-gravity planets.
A Skimmer could decrease the duration of a Basic Lashing by increasing their own weight.
== Hemalurgic Use ==
When used as a Hemalurgic spike, iron steals physical strength. Increasing the number of spikes increases the strength of the recipient, but at the cost of twisting the body and mind of the person who receives the spikes.
=== Hemalurgic Constructs ===
Koloss are created when a living human is implanted with four iron spikes. This gives the koloss incredible strength, but the process effectively destroys their minds, leaving them incapable of complex logic and extremely vulnerable to Ruin's control.
=== Kandra Blessing ===
The kandra can use a pair of these spikes as a Blessing and call them the Blessing of Potency. Like all kandra Blessings, the Blessing gives the mistwraiths sentience, with the added benefit of physical strength and endurance. It is similar to an Allomancer burning pewter, however the added strength and endurance cannot be regulated or changed.
== Fabrial Use ==
A fabrial with an iron cage will physically attract the element corresponding with the trapped spren, creating an attractor fabrial. For example, a fabrial that draws nearby smoke and causes it to accumulate near the device.
== Aetheric Use ==
Putting an iron tool near a growing aether substance pulls the substance in towards the tool as it grows.
== Notes ==
es:Hierro