I received an email with the following sentence:
The meetings will be discussing on this early next week.
I have two questions:
Should we use will discuss rather than will be discussing? I don’t know the purpose of the future continuous here, or the general purpose of the future continuous tense.
Should we use will discuss the matter or will have discussion on this matter (I guess that was a mistake to use will discuss on here)?
Will be discussing this would work. There is some time in the meetings next week when we will, in fact, be discussing this.
Either will discuss the matter or will have a discussion on the matter is correct. But they have slightly different connotations: will discuss could span some time, while will have a discussion refers to a particular discrete event.
Will be discussing on this, as you have said, is incorrect.
There’s another issue here which you have not asked about: a native speaker would be rather unlikely to say that a meeting will discuss anything, since it is not a person. The phrasing would more likely be we will discuss this in the meetings, or perhaps the meetings will include a discussion on this, or something to that effect.