Past Modals vs Perfect Modals

[Folkas]

Hello. I found myself lost in modal verbs. I can't find difference between Past Modals and Perfect Modals.

For example:

How could it be?

How could it have been?

How and where should I use perfect and past tenses?
Thank you!

[Raymott]

Hello. I found myself lost in modal verbs. I can't find difference between Past Modals and Perfect Modals.

For example:

How could it be?

How could it have been?

How and where should I use perfect and past tenses?
Thank you!

I'm not sure your conception is right. The modal verb 'could' is the same and has nothing to do with the difference in these sentences.
It might be easier for you to concentrate on the real difference, which is "be" in the simple present tense and the present perfect tense.

1A: It is [raining, stupid, amazing, the truth ... ].
1B: How could it be?

2A: It was [raining, stupid, amazing, the truth ... ]
2B: How could it have been?