Bill and Ted are high school buddies starting a band. They are also about to fail their history class—which means Ted would be sent to military school—but receive help from Rufus, a traveller from a future where their band is the foundation for a perfect society. With the use of Rufus' time machine, Bill and Ted travel to various points in history, returning with important figures to help them complete their final history presentation.

Amiable slackers Bill and Ted are once again roped into a fantastical adventure when De Nomolos, a villain from the future, sends evil robot duplicates of the two lads to terminate and replace them. The robot doubles actually succeed in killing Bill and Ted, but the two are determined to escape the afterlife, challenging the Grim Reaper to a series of games in order to return to the land of the living.

Yet to fulfil their rock and roll destiny, now middle-aged best friends Bill and Ted set out on a new adventure when a visitor from the future warns them that only their song can save life as we know it. Along the way, they are helped by their daughters, a new batch of historical figures and a few music legends — to seek the song that will set their world right and bring harmony to the universe.