You add fuel to the fire when you do something that makes a bad situation worse. Example: "When those two are fighting, I don't get involved. It only adds fuel to the fire."

A conflict between two people is like a fire, with both people adding "fuel" to the fire. You add fuel to the fire when you do something that makes the conflict worse. Example: "I wanted to help, but I was afraid I would add fuel to the fire."

Adding "fuel" (such as wood or gas) to a burning "fire" makes the flames burn even higher and brighter. Sometimes you get involved because you want to help, but your involvement only makes the problem worse, adding fuel to the fire. Example: "Please don't talk to him when he's in a bad mood. It just adds fuel to the fire."