Semi-modal verbs or semi-modal auxiliary verbs are so-called because they can function as modal auxiliary verbs as well as main verbs. Semi-modal verbs combine with the preposition to to express about the same things as the main modal verbs. The bare form of the main verb always follows the semi-modal verbs which are had better, ought to, used to, dare, and need. Semi-modal verbs are used with main verbs, but they cannot be used as main verbs by themselves.

Semi-modal verbs do not have simple past tense, present participles, or past participles. They cannot be used to form infinitives with the exception of ought to and used to. Both these verbs are always followed by infinitives.  When a semi-modal verb is used with a third-person singular subject, it does not change its form.

Had better
Had better is used to issue warning, give advice, make suggestion, recommend an action that will avoid  something bad that is likely to happen, or to say something that should be done or is worth doing in a particular situation. The verb had of had better cannot be changed to have. It is always had. It can be contracted to You’d better . . .
 
We use had better for the present and future, but not the past. The present continuous tense is not used with had better.
 

Examples:

  • You had better ( ‘d better) go now before the store is closed. (Present)
  • We had better get up early tomorrow. We are going to leave early. (Future)
  • Not: She had better watched the documentary last night. (Past)
  • Not: You had better stopping the car at the roadside. (Present continuous)

 

The verb that follows the modal verb had better is always in the simple present tense.

Examples:

  • We had better go by taxi.
  • You had better clear up the mess before mum returns.
  • At your age, you had better have regular check-ups.

 

The main modal verbs should and ought to can be used to replace had better without affecting the meaning.

Examples:

  • You are coughing loudly.
  • You had better see a doctor.
  • You should/ought to see a doctor.
  • I think I'm overeating.
  • I think I had better go on a diet.
  • I think I should/ought to go on a diet.
  • We tell her not to befriend him. He's a drug addict.
  • We tell her she had better not befriend him. He's a drug addict.
  • We tell her she should not/ought not to befriend him. He's a drug addict.

 

‘Had better’ used in question and contraction
The modal verb had better has its negative form with the word not following it: had better not

 

Examples:

  • I had better not arrive late if I want to have a seat.
  • You had better not use the device without reading the instructions.
  • We had better not drink too much tonight.

 

Questions using ‘had better’
In questions using had better, the subject comes between them. Negative questions will have had not in contracted form coming before the subject.
 

Examples:

  • Had you better write down my phone number before you forget it?
  • Had we better stop arguing so much over such a small matter?
  • Hadn’t they better let us know if they are coming?
  • Hadn’t we better inform them where we are going?