- "No, no, that's just a prototype."
"What's it made of?"
"Vibranium. It's stronger than steel and a third of the weight. It's completely vibration absorbent."
"How come it's not standard issue?"
"That's the rarest metal on Earth. What you're holding there, that's all we've got."
- ―Howard Stark and Steve Rogers
Vibranium is a very rare element that was first discovered by researchers during the early 20th Century. Vibranium is a nearly-indestructible metal, which makes it highly sought after. Most notably, Captain America's Shield is made completely out of vibranium. The metal has only been found in Wakanda.
Captain America's Shield
- "The most versatile substance on the planet, and they used it to make a frisbee."
After successfully proving himself as a soldier in the battlefield, Steve Rogers was taken to a U.S. Army facility. He entered Howard Stark's workshop where Stark presented him with different types of shields to adopt as his main weapon as Captain America. Rogers was intrigued by a silver, circular shield lying on a shelf. Stark informed him that its unique vibranium composition makes it lighter and stronger than steel, and nearly indestructible. He also added that the shield had been forged out of their entire vibranium stockpile. 
CXD 23215 Airborne Mobile Command Station
S.H.I.E.L.D. Director Nick Fury used vibranium to make the Toolbox, a compact digital storage device that holds a collected database of classified S.H.I.E.L.D. files, and additional information, privy to any acting Director of S.H.I.E.L.D. He gave this Toolbox to Phil Coulson after making him the new director, telling him that the toolbox would help Coulson rebuild S.H.I.E.L.D.
In order to find the Toolbox Alphonso Mackenzie placed a scanner programmed to find anything with vibranium in the engine of little Lola. With the information of the scanner Bobbi Morse was able to locate and take the Toolbox to Robert Gonzales.
Since Phil Coulson was unwilling to open the Toolbox for Gonzales, the device was given to Anne Weaver to crack. Unable to crack it herself, she asked Leo Fitz to help her. During his research on the Toolbox he was unable to find any ports or external power sources in the pure vibranium box. He also found that there were pores in the vibranium which were constantly shifting.
In their last hope to open the vibranium box S.H.I.E.L.D. flew in a state-of-the-art, next-gen fiber laser from the Iliad to the Playground to cut through the vibranium and finally figure out the truth.
Ultron's New Body
During an attempt to create a more powerful body, Ultron manipulated Doctor Helen Cho to use the Cradle for the creation of his new body. Under the control of the Scepter, she used the machine to create the body, combining artificial organic tissue with Vibranium samples that Ultron had stolen from Ulysses Klaue. When the Avengers arrived aiming to stop him, Ultron was forced to flee before he could finish uploading his mind into the body.
During a chase through the streets of Seoul, the Cradle was juggled around until it was recovered by the Avengers and taken to Avengers Tower in New York City. Upon examination, Tony Stark chose the idea of repurposing the body rather than destroying it like the majority of the team desired would be a more beneficial choice. He convinced a reluctant Bruce Banner to help him achieve this, and together, the two uploaded the recently recovered J.A.R.V.I.S. A.I. into the body, thus creating Vision.
With Ultron's plans of creating a perfect form being thwarted, he decided on a compromise in which he used parts of the remaining vibranium to create a more durable robotic body while using the rest of the vibranium to strengthen the core structure of his device. To terrify Romanoff, Ultron ripped apart his current body and showed her his new upgraded form before leaving her locked in a cage to die in the ensuing battle.
Ultron made plans for global extinction since his creation, which consisted of a combination of vibranium and Chitauri technology to create an extinction-level event. To that end, he sought out Ulysses Klaue, who had smuggled large amounts of the metal from Wakanda. Either buying or stealing a large amount of it, Ultron used the metal to start building a new, synthetic body for himself, with the assistance of Helen Cho's Cradle. This body would later become the Vision. Though he lost the body to the Avengers, Ultron had enough vibranium left over after creating his doomsday device to build a completely new body for himself.
As the king and protector of Wakanda, the ruler is crowned with a ceremonial regalia in the form of a Vibranium laced-panther habit. The vibranium in the suit allowed it to be at least somewhat bulletproof and allow the user to be seemingly unfazed when being struck by bullets. The suit has fingernails made of vibranium which can be retracted. The fingernails are shown to be able to cut through almost anything, and was able to create a notable scratch on Captain America's shield. T'Chaka, the King of Wakanda took the role as the Black Panther in his youth until he became too old. His son T'Challa would later take over his father's mantle as the protector of Wakanda in his place.
Vibranium is an extremely rare element that possesses unique attributes. In a pure mass, vibranium forms a solid metal that is stronger than steel, but only a third of the weight, as well as being completely vibration absorbent. This makes the material nearly indestructible, as any attempt to physically damage the material will be negated on a molecular level as mechanical/kinetic energy will be absorbed instead of breaking any bonds in its molecular matrix. In general, this means that vibranium can absorb a wide variety of physical impacts, including high-caliber bullets, without taking any damage or weakening. 
Vibranium also deflects kinetic energy. Captain America's vibranium shield for example, was able to deflect high-caliber bullets (making them crumple on the impact), Iron Man's repulsor beams (by having them ricochet into enemy Chitauri), and even an impact from Mjølnir itself (in a form of a massive shock-wave that sent Thor flying back). Captain America's shield has also been known to be thrown at high velocities without being affected by wind resistance, and is able to ricochet off of multiple surfaces.
However, despite its near-indestructible nature, vibranium's durability ultimately has its limits - the energy projected by the Infinity Stone in Vision's forehead combined with Iron Man's repulsors and a lightning bolt from Mjølnir was able to slowly melt away Ultron's vibranium outer shell. Scarlet Witch was also able to break through the metal with her telekinesis.
Vibranium has magnetic properties, as Bobbi Morse used her battle staves to procure the Toolbox from its container with magnetism and Captain America's Shield could return to his arm by using a magnetic device.
|Appearances for Vibranium|
In chronological order:
- In the Iron Man 2 novelization, the element created by Tony Stark to replace Palladium in the Arc Reactor is called Vibranium. The subsequent release of Captain America: The First Avenger retcons that information.
- ↑ Captain America: First Vengeance
- ↑ 2.0 2.1 Captain America: The First Avenger
- ↑ Agents of S.H.I.E.L.D.: 1.08: The Well
- ↑ Agents of S.H.I.E.L.D.: 1.22: Beginning of the End
- ↑ Agents of S.H.I.E.L.D.: 2.11: Aftershocks
- ↑ 6.0 6.1 Agents of S.H.I.E.L.D.: 2.15: One Door Closes
- ↑ Agents of S.H.I.E.L.D.: 2.18: The Frenemy of My Enemy
- ↑ 8.0 8.1 8.2 8.3 8.4 Avengers: Age of Ultron
- ↑ Captain America: Civil War