Which particles constitute the electric current in a metallic conductor?

Hint: We know that conductors are the material which consists of movable electric charges. There are two types of conductors, one is electrolytic and another one is electrolytic conductors. Here we are talking about the metallic conductors where the metal contains free charges for the conduction of electricity.

Complete step by step solution:
An electric current flows through conductors only when electrons move through the conductor. The electricity will pass through the metallic conductors as the negative charge flows through it and that negative change is the electrons. And we know current is the flow of charge from the positive terminal of the conducting wire to the negative terminal.
Now in the absence of any externally applied emf that is battery, then the free electrons move randomly through the metal from one point to another that gives us a zero current.
The best metallic conductors are copper, silver, tin, graphite etc.
From the above discussion we can calculate that the particles that constitute the electric current in metallic conductors are the negative charge that is the electrons.

Additional Information:
The materials or substances that do not allow any passage of current through it are non-conductor or in other word it is called an insulator such as wood, plastics etc.

Note:
Remember that metals are better conductors than any other. They are good conductors for the thermal energy because their delocalized electrons transfer energy. Keep in mind that they have a very high melting and boiling point because of their strong metallic bonds.