Iron used to repel spirits
In theory, if ghosts do exist and they do use electromagnetic energy to manifest, then hypothetically one could use a conductor of electricity, such as iron to drain or ground out the energy from the spirit. Therefore, touching a grounded, iron object to the spirit itself would drain all usable energy from that spirit. Based on this theory, many cemeteries are enclosed by iron fencing to keep the spirits in. Also, it has been said than an iron horseshoe placed at your front door will bring good luck by keeping evil spirits out.
Sam and Dean feel cold iron is the best way to repel a spirit. They usually employ fireplace pokers, and on at least one occasion a wrench. Their hunting relatives also made use of iron. A house belonging to the Campbells, Mary's family, was outfitted with iron fixtures. John owned an iron axe that is eventually used by Sam to behead Leshii.
Sam and Dean gain firsthand knowledge of the effect of iron on spirits when they astral project with the assistance of Pamela Barnes in 4.15 Death Takes a Holiday. They find themselves trapped when a demon, despite being burned by the metal itself, encircles them with an iron chain.
- 1 Episodes
- 1.1 1.17 Hell House
- 1.2 1.18 Something Wicked
- 1.3 1.19 Provenance
- 1.4 2.06 No Exit
- 1.5 2.21 All Hell Breaks Loose: Part One
- 1.6 2.22 All Hell Breaks Loose: Part Two
- 1.7 4.01 Lazarus Rising
- 1.8 4.02 Are You There, God? It's Me, Dean Winchester
- 1.9 4.06 Yellow Fever
- 1.10 5.10 Abandon All Hope...
- 1.11 6.09 Clap Your Hands If You Believe...
- 1.12 6.18 Frontierland
- 1.13 7.07 The Mentalists
- 1.14 7.10 Death's Door
- 1.15 7.23 Survival of the Fittest
- 1.16 9.14 Captives
- 1.17 10.16 Paint It Black
- 1.18 10.19 The Werther Project
- 1.19 10.21 Dark Dynasty
- 1.20 10.22 The Prisoner
- 1.21 10.23 Brother's Keeper
- 2 Wrought Iron Lore
- 3 References
Sam uses an iron poker to repel Melanie Merchant.
The phoenix Elias Finch was unable to escape from the jail or handcuffs because they were made of iron.
When Melanie Golden and Camille Thibodeaux are being attacked by the ghost of Margaret Fox, Sam tells Melanie to find some iron. Melanie grabs a fire poker, but is knocked out Margaret and is unable to use it against the ghost.
As Bobby lays dying in a hospital bed, he travels through his subconscious, reliving various memories. In one memory he is attacked by Lara Coggins, a vengeful spirit. Before she can kill Bobby, Rufus dissipates her with iron.
When is possessing the motel maid Louise, Bobby attempts to pick up a mallet from the back of a pickup truck, however it is iron and causes Bobby's ghost to leave Louise's body.
When the lights in the Bunker begin to flicker, indicating a haunting. Sam rushes to the main room and sees one of the chairs spinning on its own, he grabs a iron sword from the wall and we see the apparition slowly walking behind him. Before Sam can swing around the apparition is blown away by Dean.
Rowena is still chained up in iron shackles, which she claims are diminishing her capacity to translate the Book of the Damned.
Rowena is still chained up in iron shackles, much to her chagrin.
When Rowena performs the spell to remove the Mark of Cain, the shock wave is so great that it allows her to be freed of her iron shackles, and perform magic at her full power. Freezing Crowley and Castiel where they stand, she performs the impetus bestiarum spell on Castiel, and orders him to attack Crowley.
Wrought Iron Lore
Wrought iron is sometimes asserted to repel, contain, or harm ghosts, fairies, witches, and/or other malevolent supernatural creatures. This belief continued into later superstitions in a number of forms:
- Nailing an iron horseshoe to a door was said to repel evil spirits or later, to bring good luck.
- Surrounding a cemetery with an iron fence was thought to contain the souls of the dead.
- Burying an iron knife under the entrance to one's home was alleged to keep witches from entering. 
Cold iron is also used for similar purposes. However, cold iron is pure iron that is not smelted out of ore, but hammered pure without melting.