In normal melting there is no significant change in the electronic structure, while in anomalous melting the crystal and liquid have different electronic structures. For those elements that melt normally at zero pressure, the pressure derivative of the melting temperature is shown to follow the normal melting rule. For Ar, Na, K and Hg, the normal melting properties continue to hold to high compression, and in Hg it appears that the strong higher-order correlations in the liquid are gradually weakened by compression. The normal melting process is described by two sets of nearly independent parameters: universal statistical factors, and factors depending on the interatomic forces. Anomalous melting is related to a compression induced solid-solid-liquid triple point, and Cs is observed to change from normal to anomalous as its first triple point is approached.