Future "be about to"

Formula:

am / is / are + about to + V (infinitive)

For example: I am about to leave.

Subject + am / is / are + about to + base verb.

Example 1 (very near future):

The train is about to leave.

Example 2 (about to happen):

Look out! You are about to fall.

Example 3 (immediate action):

We are about to start the meeting.

Be about to vs Be going to

Be going to describes plans and intentions. Be about to means the action is immediate.

Example: I am going to start a new job (future plan). I am about to start work (right now).

Be about to vs Future Simple (will)

Will can refer to general future actions. Be about to focuses on something about to happen at this moment.