Can you touch a car battery with a wrench?
only if it's off
The plastic body of the battery, or one of the terminals, yes,
BUT... disconnected from the vehicle or not, DO NOT allow any
metallic object to touch BOTH of the battery's terminals [Positive
and Negative] AT THE SAME TIME.
This is because that touching both terminals at the same time
with any conducting metal such as a wrench will create a SHORT
CIRCUIT, and COULD cause the battery to explode, throwing shrapnel
and battery acid everywhere for several feet around the shorted
battery.