Introduction:
In the field of electrical engineering, permittivity is a measure of a material's ability to store electrical energy in an electric field. It is denoted by the symbol ε (epsilon) and is a fundamental property of materials. Permittivity determines how much electric flux can be generated in a material under the influence of an electric field. There are different types of permittivity, including absolute permittivity, relative permittivity, and total permittivity.

Absolute Permittivity:
Absolute permittivity, also known as the electric constant or vacuum permittivity, is a fundamental constant of nature denoted by ε0. It is the permittivity of free space, vacuum, or air. The value of absolute permittivity is approximately 8.854 × 10^-12 farads per meter (F/m).

Relative Permittivity:
Relative permittivity, also known as dielectric constant or electric constant, is a measure of how much a material can store electrical energy compared to vacuum or air. It is denoted by εr. The relative permittivity of a material is a dimensionless quantity, and it indicates the factor by which the electric field in the material is reduced compared to the electric field in vacuum or air. Relative permittivity is specific to each material and can vary depending on factors such as temperature and frequency.

Total Permittivity:
The total permittivity, ε, in metals is equal to the absolute permittivity, ε0. In other words, metals have a relative permittivity of unity (εr = 1). This means that the electric field in a metal is not reduced compared to vacuum or air. The total permittivity of a metal is the same as that of free space or vacuum.

Explanation:
Metals are conductive materials that contain a large number of free electrons. These free electrons are highly mobile and can move easily in response to an applied electric field. As a result, metals have very high electrical conductivity and low resistance. The presence of free electrons in metals allows for the rapid flow of electric current.

In metals, the free electrons essentially screen the electric field, preventing it from penetrating deep into the material. This phenomenon is known as the skin effect. Due to the high electrical conductivity of metals, the relative permittivity is very close to unity, and the electric field is not significantly reduced.

Therefore, the total permittivity in metals is equal to the absolute permittivity or the permittivity of free space. This means that the electric field in metals is not affected by the presence of the material, and the total permittivity is the same as that in vacuum or air.

In summary, the total permittivity in metals is the absolute permittivity or the permittivity of free space (ε0) because metals have a relative permittivity of unity (εr = 1).