English has many ways to express the future, with subtle differences. For example:
1. I will meet her tomorrow.
2. I am meeting her tomorrow.
3. I am going to meet her tomorrow.
4. I am to meet her tomorrow.
5. I shall meet her tomorrow.
6. I will have met her tomorrow.
7. I will be meeting her tomorrow.
8. I am about to meet her tomorrow.
9. I might meet her tomorrow.
10. I may meet her tomorrow.
What’s the difference? Note that some expressions can carry more than one meaning.
1. Simple statement of the future. Prediction of an event not already decided or obvious. Announcement of a decision. Threat. Promise. Command.
2. Something already planned, arranged, or decided.
3. Something already planned or previously decided; emphasis on the idea of intention. Prediction about an event outside of one’s control.
4. Scheduled event.
5. Simple statement of the future more common in British than American English. Obligation.
6. Prediction about a completed action at a certain time in the future.
7. Fixed or decided future event, but without a sense of personal intention.
8. Future event very close to occurring in a real or emotional sense.
9. Prediction; unlikely possibility.
10. Prediction; likely possibility.
There’s more to say about future expressions in English, but this covers the main points. I teach English as a second language, and I have to teach these fine distinctions to my students. Native speakers usually know English by memory: they remember words in use rather than thinking through rules, and they understand the meaning by repeated example.
Memory as a grammar guide only works if you’ve been exposed to a lot of accurately used English, so knowing the rules helps ensure precision. It can be dangerous to write on automatic pilot.
— Sue Burke