Since Yee's seminal work the finite-difference time-domain (FDTD) method has attracted tremendous interest for the investigation of electro-dynamic problems. One of the current applications is the simulation of metallic structures in the context of realizing optical components with dimensions smaller than the wavelength of light, often referred to as the field of plasmonics. This article provides an overview of the literature on the FDTD method with regard to the simulation of metallic frequency dispersion. Focus is laid on the modelling of the frequency dependent character of the dielectric function of metals. Two independent fitting algorithms are described and applied to describe the real and complex susceptibility function of metals. Dispersive models for nobel metals commonly employed in FDTD simulations are compared and their implementation in the FDTD method is presented.