I need to run 80 feet of electrical wire underground from my main panel from my house to a panel in my garage. I want to have 80 amps in the garage. What would be the proper type of wire I should use. I haven't decided on copper or aluminum. I guess whatever I can afford. I was also wondering about conduit thickness if necessary. Any help would be appreciated. This is in America.

In theory, you can use #4/3 AWG UF cable.

This would allow you to direct bury the cable. #4 AWG is rated at 100 amp.

Also, at the sub panel, you will need to sink at least on ground rod. Connect the sub panel, ground bus bar and ground rod together. The Neutral (White) conductor must be electrically insulated from the sub panel's grounding.