Final answer:
Free electrons in conductors such as metals move through the material when an electric field is applied, resulting in a flow of electric current and the generation of thermal energy, as opposed to insulators where charge movement is restricted.
Step-by-step explanation:
When electrons move freely from one electron cloud to another, it is a characteristic of substances known as conductors. In the case of metals, this occurs because some of the electrons in the material, known as 'free electrons,' are not tightly bound to individual atoms but can move throughout the metal's atomic lattice. When an electric field is applied, these electrons accelerate and drift, causing a flow of electric current. During this movement, the electrons frequently collide with the lattice's atoms and other electrons, which results in the generation of thermal energy and an increase in the temperature of the conductor. This electron mobility is crucial for the electrical conductivity of materials and is in contrast to insulators, where such movement of charges is highly restricted.