In this PhD thesis, the optical spectra of a variety of metals are investigated. The optical spectra are determined within the independent-particle approximation (IPA) using Kohn-Sham orbitals and eigenvalues. In some cases, the random-phase approximation and the adiabatic local-density approximation are used. A detailed analysis of the origin of the spectral features as well as a comparison of theoretical and experimental spectra helps to identify sources of discrepancy between theory and experiment. This allows for a judgement to which extent the IPA based on the Kohn-Sham band structure yields reasonable results. The following aspects related to optical properties are investigated in this PhD thesis: For Pd, the origin of optical excitations is studied in detail for zero momentum transfer. Thereafter, the evolution of the momentum-dependent electron energy-loss spectra is examined for increasing momentum transfer in (100), (110), and (111) direction. The optical properties of bulk Al are explored at ambient conditions and for increasing pressure. In case of Al(001) thin films, the focus lies on the impact of growing film thickness and of corresponding surface bands on the imaginary part of the complex dielectric function. The influence of spin-orbit coupling on the optical spectra is discussed for Au, Pt, Pb, and W. For Au, the spectra obtained from a non-relativistic and a scalar-relativistic treatment are calculated for comparison. Calculations of the complex dielectric function and reflectivity are carried out for Ag, Cu, Ni, Fe, Mo, Ta, V, Co, Ti, Zn, Bi, and Te, representing benchmark data for the IPA based on the Kohn-Sham band structure.