Nth metal (also called ninth metal) is a metal found in the DC Universe.
It is native to Thanagar, the home planet of Katar Hol, Shayera Hol, and Shayera Thal. Among the unusual properties of Nth metal is the ability to negate gravity, allowing a person wearing an object, such as a belt, made of Nth Metal to fly. In addition, Nth metal also protects the wearer from the elements and speeds the healing of wounds, increases their strength, and protects them from extremes in temperature.
It has many other properties that have yet to be revealed in full. It has been implied that the apparently " magical" abilities of the Thanagarian supervillain, Onimar Synn, all stem from his unique mastery of the properties of Nth metal. These powers are augmented to a god-like level in the Rann-Thanagar war when he builds himself an artificial body made of the substance.
In ancient Egypt a Thanagarian spaceship made of Nth metal crash-landed, to be discovered by Prince Khufu and his betrothed, Chay-ara. Exposure to Nth metal forced Khufu and Chay-ara into a cycle of reincarnation. In the Twentieth Century, they were incarnated as Carter Hall and Shiera Saunders, the original Hawkman and Hawkgirl. As Hawkman and Hawkgirl, they wore Nth metal belts, made with the help of Thanagarian Paran Katar, father of Katar Hol, when he was visiting earth.
Many years later, Carter and Shiera's son, Hector Hall made a suit of armour made of Nth metal and took the name Silver Scarab as a founding member of Infinity, Inc. The suit provided him with protection from attacks, allowed him to fly and to project solar energy blasts, and let him lift great weights.
The current Hawkman and Hawkgirl continue to wear Nth metal as does Deathstroke within the New 52.
Members of the Legion of Super-Heroes wear Flight rings made of an alloy of Nth metal called Valorium.
In some other publishing's Nth Metal has the capacity to destabilize magic and all things wrought of it, it's mainly utilized by Thanagarians in JLU continuity but has been used by both Batman and Green Arrow against they're more supernatural foes.