The film is about to start.

phrase
be  about to do (something)
for talking about the immediate future

About to is not a tense. It is a special structure that we use to talk about the immediate  future. If you are about to do something, you are going to do it very soon.

What is the structure of  about to?

The structure of about to is:

subject+be+about to+base verb
The filmisabout tostart.

In this structure the verb be is conjugated (for example, am, are, is). The base verb does not change of course. Look at these examples:

subjectbeabout tobase verb
Iamabout toleave.
Youareabout todiscover.
Itisabout toend.
Weareabout toeat.
Theyareabout topay.

How do we use  about to?

We use about to when something is going to happen very soon, sometimes immediately . Look at these examples:

  • Can I call you back? I'm¬†about to¬†go out.
  • Look at that monkey! It's¬†about to¬†jump.
  • Hurry! The shop's¬†about to¬†close.
  • The sky is dark. I think it's¬†about to¬†rain.
  • Turn off your phone. The concert is¬†about to¬†start.
  • We're¬† about to¬†have lunch. Would you like to join us?

about to with different tenses

The examples above are with the present simple tense (am, are, is). But we can also use about to with the past simple tense (was, were) and the future simple tense (will be). For example:

  • I had to hurry. They¬†were¬† about to¬†close for the night.
  • He¬† was¬† about to¬†leave when the phone rang.
  • The sun¬†was¬† about to¬†disappear behind a cloud.
  • I¬† was¬† about to¬†call John when he called me instead.
  • You'll disturb her if you call at 9:30 tonight. She¬†will be¬† about to¬†go to bed.
  • This time tomorrow we'll be¬† about to¬†land at Heathrow Airport.

Occasionally we may use about to with more complex tenses such as present perfect and  past perfect, or with modals like could and might , as below:

  • I 've been¬† about to¬†contact you several times and each time something happened to change my mind.
  • She¬† had been¬† about to play the piano, but she stopped, afraid she might disturb the neighbours.
  • I have a feeling that my husband¬†may be¬† about to¬†leave me.
  • According to the police he¬†could have been¬† about to¬†carry out a major terrorist attack.
  • He was afraid the lion¬†might have been¬† about to¬†attack him.

about to with "just"

We can stress how quickly the action is coming by adding "just " in front of about to, for example:

  • Sit down! It's¬†just ¬†about to start!
  • I was¬†just ¬†about to go to bed when the police knocked at the door.
  • She was¬†just ¬†about to open the door when the phone rang.

about to - Remember that "very soon" is relative.

As you see above, we use about to for actions coming very soon (usually within minutes or almost immediately). But "very soon" can be relative . It depends on the overall action or "story". If we are talking about a story over several months or years, then "very soon" could be a few days or weeks. Look at these examples:

  • The two companies have been negotiating for six months and are now¬†about to¬†sign a contract.
  • After leaving Earth five years ago, the Juno probe is¬†about to¬†begin its orbit around the planet Jupiter.

about to with "not"

Using not with about to can have two  meanings. You will usually understand the meaning from the context:

1. normal negative  meaning, for example:

  • Are you about to eat? / No, we're¬†not about to¬†eat but we are about to watch TV.

2. indicate unwillingness  (typically AmE), for example:

  • They know they're wrong but they're¬†not about to¬†admit it.
  • I have never cooked for myself in my life and I'm¬†not about to¬†start now.
  • I wasn't about to¬†pay $20 for some junk worth 5 cents.
  • The government was¬†not about to¬†negotiate with terrorists.

about to with questions

To make questions with about to, the subject and verb  are reversed, as usual with be  questions, for example:

  • Were they¬†about to¬†leave?
  • What are you¬†about to¬†do?
  • Are you¬†about to¬†go to bed?
  • Why are they¬†about to¬†close down?
  • Will they be¬†about to¬†arrive at that time?
  • Had they been¬†about to¬†attack?
  • Could they be¬†about to¬†release him?

Example sentences

Here is a mixture of typical sentences using about to made with various tenses:

  • You must keep what¬†you are about to¬†learn to yourself.
  • It's 8.25! You're about to miss your train!
  • I crashed the company car. My boss is not about to give me a pay raise.
  • They're about to emigrate to Australia. I think they'll be gone by next week.
  • It seemed that she was about to cry.
  • We were about to give up when a fantastic new order came through.
  • Wasn't he just about to pay?
  • I'm not about to let you get away with that.
  • As the lift door was about to close, someone pushed the open button outside.
  • The police showed up at the farm just as they were about to begin milking the cows.
  • Anthony is about to begin a programming course and hopes to become a software engineer when he graduates.
  • They are about to get married. I think it's next week.
  • What I am about to tell you is top secret.
  • The story¬†you are about to¬†read is an absolute classic.
  • Prepare yourself. What¬†you¬†are¬†about¬†to¬†see¬†will shock you.
  • The sun was about to come up when we went to bed.
  • He could have been about to shoot.
  • They might have been about to attack.
  • And with him is Donald Trump whose picture¬†you¬†are¬†about¬†to¬†see.
  • Are the Smiths about to go on holiday?
  • Ram was about to turn on his PlayStation when his girlfriend called.
  • I had been just about to water my plants when funnily enough it started to pour with rain.

sources : Original Link