A metal is a giant structure. Its atoms lose their outer-shell electrons, leaving a regular arrangement of positive ions in layers. The outer electrons are delocalised, which means they are not fixed to any one atom and can move freely through the whole structure. Metallic bonding is the strong electrostatic attraction between the positive ions and the delocalised electrons.
Metals conduct electricity, whether solid or molten, because the delocalised electrons are free to move and carry charge through the metal.
Metals are malleable, which means they can be hammered or bent into shape without breaking. The layers of ions can slide over each other, and the delocalised electrons still hold the ions together, so the metallic bonding is not broken. Metals also have high melting points, because a lot of energy is needed to overcome the strong attraction between the ions and the electrons.
