Household electric wires are covered in a plastic coating

Why

Samir has a fact right and a link wrong — touching a damaged wire really can give a shock, so it's natural to connect that danger to the plastic itself. But that shock happens exactly when the plastic has worn away or cracked, exposing the bare metal wire underneath — the plastic isn't the path the current takes, it's the wall stopping current from reaching your hand at all. Metals like the copper inside the wire are conductors, letting current flow through them easily; plastic, rubber and most other non-metals are insulators, blocking current almost completely. That's precisely why the coating is plastic and not, say, more metal — a metal-coated wire would carry current on its outside too, shocking anyone who touched it, which defeats the whole purpose of covering a wire. Test: cut a small bare patch of exposed copper wire (with an adult and a battery-only, low-voltage circuit) and compare touching the plastic part versus the bare metal part in that safe circuit — only the bare metal is part of the current's path. Reena is right: plastic blocks current: it's a shield, not a channel, and danger comes from where that shield has failed.