The earth wire typically is connected to the metal casing of the appliance, and the earth pin of the plug. This is a critical safety feature, which will cause the circuit protection to trip in the event of phase touching the metal of an appliance.

Connecting phase directly to the metal is an excellent way to kill someone.

https://www.rnz.co.nz/news/national/502326/nelson-electrician-stephen-burton-s-failure-to-carry-out-simple-task-linked-to-death-of-builder-craig-johnston