Conversational structures with had better

We use had better to tell people what we think they should do.

* You had better turn that music down before dad gets angry.
* You had better consult a doctor.

Had better is also used to give advice to ourselves.
* It is seven o’clock. I had better put the meat in the oven.

Had better may suggest a threat. It is not used in polite requests.
Compare:

*Could you lend me some money? (Request)
*You had better lend me some money. (If you don’t, there will be trouble.) (Order/threat)