Why can metals conduct electricty?

This is because of the special type of bonding that occurs in metals. A metal is a giant structure of regularly arranged atoms, the outermost electrons ( check they understand the differences between the subatomic particles) of these atoms is free to move about the entire structure, it is delocalised. Electricity can also be described as the flow of charge, which means it needs freely moving charged particles in order to be conducted. In a metal these free charged particles are the delocalised negatively charged electrons.