Here's why:
* Metallic Bonding: Metals have a unique structure where their outer valence electrons are loosely held and can easily move throughout the entire structure. This creates a "sea" of delocalized electrons that are shared by all the metal atoms. The metal atoms themselves lose their valence electrons and become positively charged ions. These positive ions are then held together by the electrostatic attraction between them and the sea of negative electrons.
Let me know if you'd like to know more about the properties of metallic bonding!