Experiments with magnets and conductors

Density*resistivity of materials

metal density * resistivity
aluminum 67.50
copper 141.57
silver 154.31
gold 388.53
zinc 388.94
iron 685.48
lead 2192.48
mercury 13332.68

Aluminum is by far the best, that's why it is used by the power companies for the high voltage power cables strung from tower to tower.  It is very light and a very good conductor, and inexpensive, too!  A great combination.  Copper comes next, amazing since it is denser than iron.

The units here are g/cm^3 * nano-ohm-meters.