What is metallic bonding?
Metallic bonding is the process of strong electrostatic forces of attraction between the positively charged atomic nuclei of metal ions and the negatively charged delocalised sea of electrons which are mobile and freely moving thorughout the structure.
In metallic bonding, magnesium loses 2 valence electrons to become a magnesium ion.
2 valence electrons lost from each magnesium atom delocalise to form a sea of electrons. They become mobile and can move freely throughout.
The strong electrostatic forces of attraction between the negatively charged sea of electrons and positively charged magnesium ions keep the structure together. This is metallic bonding in Magnesium.