The group of metals that are the best conductors of heat and electric current are the transition metals, specifically those found in Group 11 of the periodic table: copper (Cu), silver (Ag), and gold (Au).

Here's why:

* Free electrons: These metals have a unique electronic structure where their outermost electrons are loosely bound and can easily move throughout the metal lattice. These "free electrons" are the primary carriers of heat and electricity.

* High conductivity: The abundance of free electrons allows for efficient transfer of both heat and electrical energy.

* Other factors: Other factors like the arrangement of atoms and the purity of the metal also play a role in conductivity.

While silver has the highest conductivity, copper is often preferred for practical applications due to its lower cost and better availability. Gold is also a good conductor, but its high price limits its use.