When metal oxides are put into contact with water, they often, though not always, form metal hydroxides. The reaction depends on the element, the acidity of the metal oxide and on the physical state of the water.
It is generally the case that only weakly acidic or non-acidic metal oxides form metal hydroxides when in contact with water. The oxides that react in this way with water are called basic oxides. In addition, most metal hydroxides are formed only with cold water. Metal hydroxides break down into their constituent parts when exposed to high heat. Basic oxides generally do not form hydroxides when exposed to steam.