Gold

Gold is used for specific components such as Connectors, Switch Contacts, Relay contacts, and wires.

it is also part of the Motherboard.

Cobalt

Cobalt is an essential metal for the process of magnetic recording technology as used in data recording devices such as HDDs or magnetic tape. Its use as an alloying element and in cobalt compounds makes it a strategically important metal.

Silicon

Silicon is a material used for chips in computers.

Silicon is a 'semiconductor'. this is when a material can conduct some energy but isn't efficient.

This is also used in thermal compound. (the goop between CPU and cooler)