What do they mean by...?

Question

In time the monarchs captive are and thrall

I've analyzed the line. but i still do not understand its meaning.

Answer 1

Good question!

Answer 2

The word "thrall", used as an adjective, means "enslaved". Fletcher means, of course, that in time all things change or even become their opposite ["In time the strong and stately turrets fall,/In time the rose and silver lilies die,/.../In time the sea and rivers are made dry;", etc], even mighty kings becoming captives and slaves -- everything changing except his love for Licia ["Thus all, sweet fair, in time must have an end,/Except thy beauty, virtues, and thy friend."].

Answer 3

If you could state from where you took this quote,  maybe we will be able to help you.