Elements that form cations when compounds of it are in solution and oxides of the elements form hydroxides rather than acids in water. Most metals are conductors of electricity, have crystalline solids with a metallic luster and have a high chemical reactivity. Many of these elements are hard and have high physical strength. The metal series includes all elements of the alkali, alkali-earth, inner-transition (lanthanides and actinides series), transactinides and transition series as well as some elements of the metalloid series (elements: Ge, Sb and Po).