Firstly, I want to know whether will have and shall have are modal verbs, or do they have future perfect tenses, or both?
If these are modal verbs, can I use them in both the past and present?
Secondly, can I use may have in both the past and present?
Best Answer
Modal verbs are will, shall, and to have only, not their combination will have or shall have.
(So your another question “If these are model verbs, ...” is irrelevant.)
To answer your last question, may have is never used in the past tense, only in present or future (e.g. in the form may have to) ones.