Explain why aluminium Wires are preferred for overhead power cables?

Question

$\begin{array}{1 1} \text{Aluminium wires are less expensive than copper wires }\\ \text{Aluminium wires are have less density than copper wires } \\ \text{Aluminium wires are lighter than copper wires}\\ \text{Aluminium wires have more malleability than copper wires} \end{array}$