Modal verbs are for example may, can, must, should, need. They express an ability, permission, wish etc. to do something. (I may, can, must swim.) Many modal verbs cannot be used in all of the English tenses. That's why we need to know the substitutes to these modal verbs.
The future progressive tense indicates an action that will occur over a period of time at some point in the future. It expresses events that will last for a duration of time at some point in the future. It is also called the future continuous tense. The future progressive tense is also used in the future perfect progressive.
The simple past is a verb tense that is used to talk about things that happened or existed before now. Unlike the past continuous tense, which is used to talk about past events that happened over a period of time, the simple past tense emphasizes that the action is finished.