Of the elemental metals, silver is the best conductor of heat. It has a thermal conductivity of 235, meaning that it is able to transmit that amount of heat energy a single foot per hour per degree Fahrenheit.
Since silver is rare and expensive, the second best thermal conductor, copper, is often used instead in engineering applications. Copper has a thermal conductivity of 223 at 68 degrees Fahrenheit. At higher temperatures, its conductivity drops, but even at 1112 degrees Fahrenheit, it still has a conductivity of 204. The next best metal, gold, has a thermal conductivity of 182 at room temperature.