Future forms: I'm to… / etc

Young from South Korea writes:

Hi. I'd like to know how to use be to, especially in this way below: I'm to sleep on the sofa tonight.

I'm not sure if this example is right or not, but I hear this sort of expression pretty often. I guess it might be a future form. I'm waiting for your answer.

be to + infinitive

You're quite right, Young. This is a future form. When we say that things are to happen, we are talking about official arrangements and formal instructions that are imposed on us by other people. This structure is quite common in news reports and official notices of various kinds:

• Laboratory equipment is not to be left unattended in the science labs.
• This medicine is to be taken three times daily after meals.
• All visitors entering the hospital are to wear masks as protection against infection.
• Manchester City are to return to their famous sky-blue shirts next season after agreeing a sponsorship deal with Reebok.

It is also frequently used by parents or other responsible adults to give instruction to children:

• You are not to leave the school hall until your parents arrive to collect you.
• You're not to use your mobile phone for long conversations. It's too costly!
• I'm to clean up my room before I'm allowed to go out.
• She can go out tonight, but she's not to be late back.

be to + infinitive in if clauses

This structure is also very common in if-clauses when we are discussing pre-conditions:

• If we are to survive global warming, large-scale deforestation must be avoided.
• If he is to get into the first team, he must improve his diet and spend more time training.
• If they are to get there by nightfall, they must press on. They can't afford to hang on here, waiting for the others to arrive.

future: present progressive

Note that we normally use the present progressive for fixed plans and personal arrangements in the near future that we have decided for ourselves:

• What are we having for supper tonight? ~ I'm preparing a Thai dish: red chicken curry, yellow vegetable curry and sticky rice.
• Penny tells me you're seeing Felicity tomorrow. ~ Yes, I am. ~ Where are you meeting her? ~ I'm meeting her at school and then we're going for a coffee.

future: present simple

Note that we use the present simple for fixed arrangements when they are part of a timetable or schedule:

• When do the Easter holidays start in your school? ~ They don't start until Good Friday and they are over by Easter Monday.
• You know that David's coming down for Easter. Do you know what time his train gets in? ~ It doesn't get in until nearly midnight. Are you planning to meet him.

other immediate future expressions

be about to + infinitive

be on the point of + verb-ing

be set to + infinitive

• I was about to get into the bath when the doorbell rang.
  Is that Sarah? ~ Yes, it is. You're lucky to have caught me. I was just about to leave.
• I was on the point of handing in my notice when they offered me promotion.
• The talks are set to continue throughout next week if necessary in the hope of avoiding a strike.