At room temperature, the primary charge carriers in a conductor are electrons.
What are electrons ?
These are negatively charged particles bound to the atoms of the conductor's material . When an electric field is applied, the outer electrons in these atoms are able to move freely within the metal lattice, carrying the current.
When an electric potential difference ( voltage ) is applied across a conductor, electrons drift in response to this potential difference, creating an electric current.
This mobility of electrons in conductors is what makes them good conductors of electricity. Examples of common conductors include copper, aluminum, and silver.