Foot to the metal?

Fast. The foot is on the gas (or accelerator) pedal. The metal is the firewall of the car or truck, so 'foot to the metal' is going as fast as possible.

Edit: The more common expression is pedal to the metal. We like simple stuff that rhymes.

Sure glad someone around asks questions I can answer!

Thanks!

I too, select your answer as the best one, Roger.

Or "foot to the floor". Or "give it some wellie". (BrE)

I select this post as the best answer.

"give it some wellie"?

That dog ain't gonna hunt around here.