The surface impedance of a metal slab, in the presence of a magnetic field normal to its surface, is studied. A model Fermi surface, which exhibits realistic properties, is considered and the various modes of the electromagnetic field (helicons, Doppler-shifted cyclotron resonance, Gantmakher-Kaner oscillations) are analytically examined separately in order to gain a greater understanding of the sources of these contributions. Variations of the basic model Fermi surface are then introduced. In particular, it is shown that, for a suitably designed partially compensated Fermi surface, it is possible to obtain high-frequency helicons at reasonable magnetic fields for metallic net carrier densities. A general hierarchy of cylindrically symmetric Fermi surfaces is presented, leading to a variety of Gantmakher-Kaner contributions.