Are high-Tc cuprates unusual metals?

The unusual properties of high-temperature superconductors are reviewed. The structure and chemistry of the materials are described and the strong influence of the carrier concentration on their superconducting properties is illustrated. The temperature dependences of the resistivity, Hall effects and thermoelectric power coefficients are given. These properties distinguish the cuprates clearly from any ordinary metal known until recently. In particular the normal Boltzmann transport theory is no longer applicable. It was found that these anomalous properties of the normal phase are accompanied by superconducting order parameters of uncommon symmetry (d wave), as well as non-BCS temperature and magnetic field dependences. The observation of the normal-phase pseudogap in the density-of-states spectrum by means of specific heat and other measurements seems to offer an important way forward in understanding both the normal phase and the high-temperature superconductivity mechanism.