what is the dielectric constant of a metal

The dielectric constant (also known as relative permittivity) of a metal is infinite because the permittivity of any metal is infinite. The dielectric constant of a substance is defined as the ratio of the permittivity of the substance to the permittivity of free space. The permittivity of a material denotes its ability to store electrical energy in an electric field. The expression for dielectric constant K of any material is K = ε/ ε0 where ε is the permittivity of the material and ε0 is the permittivity of a vacuum. K is directly proportional to ε, therefore dielectric constant of a metal is infinite. The electric field inside a metal is zero, which is why the dielectric constant of a metal is infinite.