Alkali metals are group one of the periodic table. They are very highly reactive metals that aren't found in free nature. Since they only have one electron in their outer shell they are ready to lose it to form an ionic bond
Just like other metals alkali metals are ductile and very good conductors of heat as well as electricity. Alkali metals are softer than other metals and if exposed to water can explode. Even when exposed to air they react quickly and release oxides.
Alkali metals have a lower density than that of other metals. They are very loosely bound with only one valence electron. They react very well with non-metals. Best with halogens.