An often overlooked aspect of antennas is RF resistance and skin effect. RF resistance and skin effect is in addition to its DC resistance. All conductors have resistance in varying amounts, this creates losses and reduces the efficiency of the antenna. In the case of the antenna (and any other circuit) this power is lost as heat.
At radio frequencies the power doesn't use all the conductor for current flow, and the higher the frequency the less of the conductor is used. The depth of conduction for various frequencies is as follows:
Frequency 1.0  3.0  10.0  30.0  100.0 300.0 500.0
Depth (inches) .0026 .0015 .0008 .00047 .00026 .00015 .00011

Here is a list of various metals and their resistivity compared to copper. Copper has a value of 1. Silver is best with .095.
Material           Silver   Copper  Gold   Aluminum    Brass Iron   Tin   Lead   St.steel
Resistively .095   1.0        1.4 1.64            4.0  6.0     7.0  13.0     53.0

Now lets take a look at some real antenna. Take an 80 meter dipole 130' long. If it is made from #18 (.047"), its RF resistance is 5.2 ohms. Now say this is matched to a 50 ohm coaxial cable and driven with 100 watts the current at the center will be 1.41 amps. The 5.2 ohms RF resistance is loss which means that 10.5 watts is used to heating up the antenna. This is a 10% loss and the same goes for receiving. Now lets make the antenna using #4 wire (.2"). The RF resistance is now 1.2 ohms, which equates to a power loss of only 2.4 watts, much better!
Now we  will make the antenna from stainless steel of the same gauges. The #18 wire will have an RF resistance of 5.2 x 53 is 275.6 ohms. Hmmm. The #4 wire is1.2 x 53 is 63 ohms. That would make a good dummy load. So an 80 meter antenna made from stainless steel will need to be very thick and heavy. I would like to see this hanging from the corner of the house, it will probably pull it off its foundations!
How about a 5/8 wavelength on 2 meters made of #18 copper wire, its RF resistance is 0.5 ohms. But if we made it from ½" copper pipe the resistance drops to .09 ohms, much better. If the 2 meter antenna is made from 0.1" stainless steel the RF resistance is 26.5 ohms. This makes mobile whips quite inefficient. However the lossyness has the effect of increasing the bandwidth of the whip, which allows the rig to operate over a wider range of frequencies. After all it's a partial dummy load, OK for local but not for DX.
From all of this, for maximum antenna efficiency at HF use thick copper or aluminum wire, even a few insulated lengths in parallel can considerably reduce the RF resistance. Use tubing for VHF. For mobile whips it is always a compromise, perhaps copper or silver plated stainless steel, providing the plating is thicker than the skin effect depth.

My name is James Watt, Sottish inventor and mechanical engineer for which the electrical unit the Watt was named. A common misconception being that I invented the steam engine, when in fact it was as a result of the combined efforts of English engineers Thomas Savery and Thomas Newcomer. The misconception that it was I arose from the fundamental nature of my contributions to its further development.