Metals are good conductors of electricity because their atoms contain at least one free electron. They are also considered excellent heat conductors, because the metal ions in the lattice are closely packed together, and the delocalized electrons can bring kinetic energy through the lattice.
The outer electrons of the atoms in metals are part of a cloud of delocalized electrons, which are electrons that participate in the metallic bond and are not confined to a single place or atom in the metal. These electrons can move freely through the lattice of positive metal ions that comprise the metallic bonds. They get shoved away from the negative terminal and pulled by the positive terminal when the wire and cell are connected. As the electron cloud flows through the wire, the electrons continue to move randomly at higher speeds.
Free electrons enable the metals to have the ability to conduct heat and electricity well. Vigorously vibrating ions provide kinetic energy to the electrons, causing the electrons to move more quickly. Some of the electrons travel down to the colder end and bump into ions that vibrate less vigorously than the ions at the hot end. The collisions cause the electrons to lose kinetic energy and allow the ions to vibrate more vigorously. Thus, the electrons can deliver the vibrational energy to the cold end quickly due to their unrestricted movement in the lattice.