Here..... compliments of Wikipedia
Conductor materials
Of the metals commonly used for conductors,
copper, has a high
conductivity.
Silver is more conductive, but due to cost it is not practical in most cases. However, it is used in specialized equipment, such as
satellites, and as a thin plating to mitigate
skin effect losses at high frequencies. Because of its ease of connection by
soldering or clamping, copper is still the most common choice for most light-gauge wires.
Compared to copper,
aluminium has worse conductivity
per unit volume, but better conductivity
per unit weight. In many cases, weight is more important than volume making aluminium the 'best' conductor material for certain applications. For example, it is commonly used for large-scale power distribution conductors such as overhead
power lines. In many such cases, aluminium is used over a
steel core that provides much greater
tensile strength than would the aluminium alone
[1][2].
Gold is occasionally used for very fine wires such as those used to
wire bond integrated circuits to their
lead frames. The contacts in electrical connectors are also commonly gold
plated or gold flashed (over
nickel). Contrary to popular belief, this is not done because gold is a better conductor; it is not. Instead, it is done because gold is very resistant to the surface corrosion that is commonly suffered by
copper,
silver, or
tin/
lead alloys. This corrosion would have a very detrimental effect on connection quality over time;
gold plating avoids that.
http://en.wikipedia.org/wiki/Electrical_conductor