he atoms of copper contain electrons and the atoms of rubber also contain electrons. Then why does copper conduct electricity but the rubber does not conduct electricity?

The atoms of copper contain electrons and the atoms of rubber also contain electrons but copper conducts electricity while rubber doesn’t conduct electricity because copper has free electrons that are held loosely to each other by the nuclei of the atom. These freely available electrons are responsible for the conduction of electricity in copper.

Whereas in rubber the electrons are under a strong influence of the nuclei of the atoms. There are no much free electrons available for the conduction of electricity in the rubber. Therefore, the rubber doesn’t conduct electricity.