If you match them incorrectly the consequences can be quite dire, as two US motorists found out.
The incident occurred in South Carolina as Jeep owner Andrew Jernigan connected jumper cables to his friend Delaney Mills' Volkswagen Golf.
Mills had stalled in the street and Jernigan hooked up the cables incorrectly as they attempted to jump-start the Golf's battery.
The damage from the mishap resulted in both vehicles being written off.
Marc Coty, a friend of the hapless pair, commented that the damage was so severe they were unable to remove the cables and were left to watch as both vehicles were engulfed in flames.
Coty explained: "While attaching the jump cables to the batteries of the cars, they accidentally crossed the wires, attaching the positive cable to the negative terminal on the battery and vice versa.
"After Andrew started his car up, the rubber melted off of the jump cables, making it impossible to remove them from the batteries of the cars. The battery of Andrew's Jeep began to smoke," he said.
Coty added: "While calling 911 to report the case to the fire department, the battery caught flame. The fire began to spread very quickly across the entire engine of Andrew's car."
Coty said they were wary of causing an electrical fire and so did not risk pouring water onto the two vehicles.
"Within the 15 minutes that it took the firefighters to get to the scene, the flames had engulfed about three-quarters of Andrew's car and the flames reached probably 10 feet (3m) in height," he added.