- be about to + verb (almost immediately)
The train is about to leave.
- be due to + verb (a fixed or expected time)
The train is due to leave at 4.30 p.m.
- be supposed to + verb (should)
The course is supposed to start at 8 o’clock, but the teacher is late again.
- be sure to / be certain to + verb (certain)
He left the office late, so it’s sure to arrive late.
He left the office late, so it’s certain to arrive late.
- be (un)likely to + verb (probable or not probable)
We started the meeting late, so it’s likely to finish it late.
It’s unlikely to start it on time.
- be to + verb (often used in news reports)
We are to get a wage raise in July.
- be to + verb (strict or formal instruction, less used)
You are not to tell anyone about this.