The absorption coefficient and the dielectric function are valid descriptions for "macroscopic" electromagnetic fields, so you would not use these quantities to look at the absorption of single photons specifically. The electric field is zero inside a conductor.

For a perfect metal (infinite conduction/no scattering), the dielectric function of a metal has infinite imaginary part. Which will make the absorption coefficient infinite as well. Meaning that the electric field (from the photons) will not penetrate into the metal at all.

The absorption coefficient and the dielectric function are valid descriptions for "macroscopic" electromagnetic fields, so you would not use these quantities to look at the absorption of single photons specifically.

For a perfect metal (infinite conduction/no scattering), the dielectric function of a metal has infinite imaginary part. Which will make the absorption coefficient infinite as well. Meaning that the electric field (from the photons) will not penetrate into the metal at all.