A metamaterial is artificially designed and its properties are not found in nature. It generally gains its properties through construction rather than its composition. In fact, metamaterials are usually made from extremely interconnected bonds at the  nano level. This allows them to be used in applications that involve manipulating light, sound, vibrations, microwave radiation, or other forms of electromagnetic radiation. Metamaterials also allow an object to be lighter, more durable/flexible, or be more electrically conductive.

How Metamaterials Work
A metamaterial is generally fabricated at the nano level in a laboratory and has certain properties for specific functions. Each metamaterial molecule is carefully aligned to change the object’s denseness, permeability, permittivity, or how waves are transferred across the material.

Applications
Metamaterials have many uses and enhance the properties of nearly any object. For example, they can be used in antenna construction as they give antennas better reception and longer range. Metamaterials are also used in cloaking devices in order to make an object invisible to the human eye. They are used to make construction materials such as brick, steel, drywall, and even wood stronger and more resistant to natural elements. Likewise, metamaterials produce computer chips and microprocessors that are lighter, smaller, more durable, and more electrically conductive. Scientists have proposed that metamaterials be used to build a cloak that can bend matter around it.

Terahertz Metamaterials
A terahertz metamaterial is capable of handling terahertz radiation that is emitted in the form of infrared electromagnetic waves. This portion of the electromagnetic spectrum includes visible light, thermal energy, and mild microwave radiation. Terahertz metamaterials are best for conducting electricity and are most often used in microprocessors and electronic devices.

Photonic Metamaterials
A photonic metamaterial is one that bends light in a different way from conventional optical devices. Photonic metamaterials have a negative refractive index. That is, they cause light and other electromagnetic waves to travel around instead of pass through them or be absorbed like natural objects do. Photonic metamaterials are used in optical instruments and cloaking devices.