Normally, electrons are bound to atoms. Because electrons carry a negative charge, atoms contain positively charged particles. It is known that electrons are located near the nucleus at ‘energy levels. They’stick around’ an atom because they are attracted to its nucleus in a sense. Some materials have outer electrons that are loosely bound to atoms. It takes very little energy for them to be free to move (across atoms)
These are called the “free electrons”. They are released from their atoms by applying an external voltage. They move around being affected by the potential difference. This is the essence of ‘electric current’.
P.S. P.S. These are not classical electromagnetic attraction models.