Modals!

Modal tenses can be divided into past and present form--though some can be used in the opposing category.

1. What tense is conveyed when we use the perfect aspect with modals when dealing with past tense modals?



2. And what does it mean when I read that modals use the tense from surrounding time adverbials etc? Modals are finite, so they have their own tense. Can someone clear up my confusion please.

Thanks