1to enrage people and make matters worse
2to add oil to the fire (idiom); fig. to aggravate a situation
Example
nǐ你xiàn现zài在shuō说zhè这zhǒng种huà话，zhǐ只huì会huǒ shàng jiā yóu火上加油。
你现在说这种话，只会火上加油。
For you to come out and say that kind of thing now would just be pouring oil on the fire.