On fire means burning, and in informal speech it also means doing extremely well. The first meaning is literal and neutral: The kitchen is on fire. In the second, people say it about someone who is getting everything right today, most often in sport, games or work: Our goalkeeper was on fire tonight. This meaning is informal: fine in IELTS Speaking, but not in an IELTS essay.
When would you say on fire?
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be on fire; catch fire; set fire to + something / set + something + on fire; be on fire (informal: doing very well)
- A neighbour called the fire brigade when she saw that the car was on fire.
- Our new sales manager is on fire this month; she has already closed six deals.
- Anna was on fire in the pub quiz and answered almost every question.
What changed
First versionWhen we arrived, the old barn was in fire.
RevisionWhen we arrived, the old barn was on fire.
In fire may seem logical, since the flames surround the building, but English says on fire about something that is burning. In fire is not used. Only the preposition has changed.
On fire describes a state: something is already burning. The moment something starts to burn is catch fire: Dry grass catches fire easily. To make something burn on purpose is set fire to something or set something on fire: Someone set fire to the bins last night.
Your turn
Leo scored three goals in the first half; he was absolutely ___.
Show the answer
on fire — Three goals in one half is a clear success, so Leo was on fire, playing brilliantly. Under fire means being strongly criticised, or literally being shot at, and nobody criticises a player who scores that much.
Think of a day when everything went well for you at work, in your studies or in sport. Write a sentence with on fire in the sense of doing very well: say when it was and what exactly you did.
I was on fire last Friday: I answered forty customer emails before lunch.
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