Expanded metal is a form of metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 stock made by shearing a metal plate in a press, so that the metal stretches, leaving diamond-shaped voids surrounded by interlinked bars of the metal. The most common method of manufacture is to simultaneously slit and stretch the material with one motion. It is often shortened to exmet, which also refers to a commercial firm by the same name that manufactures expanded metal. Also referred to as perforated metal, it is a large part of the metal industry and plays a key roll in fabrication.

Expanded metal is used in grate

Grate

*A grate is a frame of iron bars to hold fuel for a fire.*It may also refer to a covering of a drain, also called a grating.*The act of using a grater, a kitchen utensil.- People :*Don Grate US sportsman....

s and in outdoor furniture (e.g. benches) or fencing. It is often used for guarding to prevent contact with hot surfaces or machinery.

Expanded metal is often used for architectural details and finds use in security applications such as in the walls of a Sensitive Compartmented Information Facility

Sensitive Compartmented Information Facility

In United States security and intelligence parlance, a Sensitive Compartmented Information Facility is an enclosed area within a building that is used to process Sensitive Compartmented Information level classified information...

because, in heavier grades, it is difficult to breach without heavy cutting equipment or explosives.