Metals are excellent conductors of electricity due to the free movement of their delocalised electrons. When electric current flows, these electrons drift in a particular direction, allowing the transfer of energy without significantly increasing the temperature of the metal. Moreover, most metals have a high melting point, so even if there's a slight increase in temperature due to resistance, it's generally not enough to damage the metal. However, it's essential to note that if the current is too strong or if there's a short circuit, the metal can indeed heat up significantly and even melt.

Alloys are mixtures of two or more metals. When different metals are mixed, the atoms of the added metal often differ in size from those of the original metal. This disrupts the regular layers of atoms in the pure metal, making it more difficult for these layers to slide over one another. As sliding layers is a primary mechanism for metal deformation, the disruption brought by these differently sized atoms increases the hardness and strength of the alloy compared to the pure metal.

The lustrous or shiny appearance of metals can be attributed to their ability to reflect light. The 'sea of delocalised electrons' on the surface of metals absorbs photons of light and then re-emits them. This absorption and subsequent re-emission of light result in the reflection of most of the light frequencies, giving metals their characteristic shine. The freedom of these electrons to move also means they can quickly respond to the electric field of the incoming light, further enhancing this reflection.

Metals generally exhibit higher melting and boiling points because of the strong forces of attraction between the closely packed positive metal ions and the sea of delocalised electrons. This strong electrostatic attraction requires a significant amount of energy to overcome. When metals melt or boil, this lattice structure has to be broken, which necessitates the input of considerable heat. In contrast, most non-metals are covalently bonded, and it's often easier to break these covalent structures or the forces between their molecules, leading to their typically lower melting and boiling points.

The reactivity of a metal can be attributed to its tendency to lose electrons and form positive ions. This tendency is stronger in metals with atoms that can lose electrons easily. The ease with which a metal atom can lose its outermost electrons depends on factors like atomic size and the energy required to remove these electrons (ionisation energy). Generally, metals in Groups 1 and 2 of the Periodic Table, like lithium or calcium, are more reactive because they have fewer outer shell electrons and larger atomic size, making it easier for them to lose electrons.