Alkali metals are very reactive and none of these metals do not occur as free metals in nature.
Alkaline metals are also do not occur freely in nature and they are also very reactive.
For alkali elements, the densities of Lithium and Sodium are less than the density of water. However, the other elements are denser than water. Many of alkali metal compounds (NaCl, KCl, Na2, CO3, NaOH) are commercially very important.
Alkaline elements in this group are denser than water.