Calcium metal is a strong silvery-white solid at normal pressure and temperature. Calcium metal reacts with the air very slowly, while it reacts faster with hot water producing pure Hydrogen gas.
Calcium metal is important to have strong and sane bones, but it's more important as Ca2+ in biochemicals rules. Calcium ion regulates the actions of nerves and muscles and it's fundamental for that reason. Calcium is the first alkali-earth metal that must be stored under an inert atmosphere or under high quality mineral oil, as we do, to prevent oxidization. In the right picture is showed a very pure sample of Calcium crystals oxide free and argon sealed.