Why can a metal carry electric current?

A metal wire carries current because some electrons can move through its structure instead of remaining confined to individual atoms. These delocalized electrons respond to an electric field. The positive ion cores stay near their positions in the solid, so conduction does not require the whole metal structure to flow down the wire.

Electrons already have microscopic motion even when there is no current. Without a directional imbalance, motions in opposite directions give no net charge flow. An applied field adds a small average directed motion called drift. Because electrons are negatively charged, their electrical force and average drift point opposite the field.

In the illustration, the field points right and electron drift points left. Conventional current points right because its direction is defined using positive charge flow. These arrows describe the same conduction process with different conventions. They do not mean that positive ion cores travel down the wire or that each electron follows a straight uninterrupted path.

Real metals resist current. Electrons interact with lattice vibrations, imperfections and other features of the material, disrupting directed motion. The field keeps supplying energy while these interactions transfer energy into the material, contributing to heating. Mobile carriers therefore make conduction possible without making resistance vanish.

An electric field can organize motion across a connected circuit while individual electrons drift slowly, so energy transfer need not wait for one electron to reach the lamp. This drawing isolates carrier directions and omits the complete circuit. Its localized-electron comparison is an ideal insulator at ordinary fields, rather than a description of every insulating condition.