Why does metal block cell phone reception

Why does metal block cell phone reception?

Sources would be helpful. Thanks :)

All matter is made up of atoms, with space in between. Metal, being dense, has less space between the atoms. With less space, the radio waves cannot go through metal. Additionally, metal attracts radio waves (that is why antennas are made of metal), which also prevents waves from passing through.

Any thick and dense materials will block the radio waves with which cell phones communicate.