Are high-T-c cuprates unusual metals?

The unusual properties of high-temperature superconductors are reviewed. Th e structure and chemistry of the materials are described and the strong inf luence of the carrier concentration on their superconducting properties is illustrated. The temperature dependences of the resistivity, Hall effects a nd thermoelectric power coefficients are given. These properties distinguis h the cuprates clearly from any ordinary metal known until recently. In par ticular the normal Boltzmann transport theory is no longer applicable. It w as found that these anomalous properties of the normal phase are accompanie d by superconducting order parameters of uncommon symmetry (d wave), as wel l as non-BCS temperature and magnetic field dependences. The observation of the normal-phase pseudogap in the density-of-states spectrum by means of s pecific heat and other measurements seems to offer an important way forward in understanding both the normal phase and the high-temperature supercondu ctivity mechanism.