A Faraday cage protects sensitive electronics from external electric fields by surrounding them with a conducting enclosure.
When an external electric field reaches the conductor, mobile charges redistribute across its surface. This rearrangement creates an opposing field that greatly reduces the field inside the enclosure. The effect works with solid metal shells and with conductive meshes, provided the openings are suitably small for the fields involved.
The concept is named after English scientist Michael Faraday, who demonstrated electrostatic shielding in the 19th century. A Faraday cage does not automatically block every electromagnetic signal: its effectiveness depends on material, enclosure continuity, frequency, and opening size. Cars and aircraft can provide useful shielding during lightning strikes because current travels around their conducting outer surfaces.