Magnesium is a metal. Specifically, it is an alkaline earth metal. Its atomic number is 12, and it was first isolated by the British chemist Humphrey Davy in 1808.
Though magnesium is abundant on the earth, it's never found in a free state. It's considered a structural metal, which means it can be used as a building material. However, its melting point is too low for it to be unalloyed with other metals. The melting point of magnesium is only 1202 degrees Fahrenheit.
As a nutrient, magnesium is essential for health. It supports the functioning of the heart, nerves, muscles and immune system.