One morning we came late, and the
eggs were already eaten.     (And the cat had departed.)

Past Continuous:
(O + WERE/WAS + BE + ING + V3)
Eggs were being eaten all day. (are you getting sick of eating eggs yet?)

Past Perfect:
(O + HAD + BEEN + V3)
Eggs had been eaten for years.

And lastly,

Will eggs be eaten in the Future?
(WILL + O + BE + V3)

Yes, eggs have a future. In this case, you will use the BE (state) verb again.
(O + WILL + BE + V3)
Eggs will be eaten in the Future.  (by us, by the cat, by the world of our children)(bye bye)

                                                        End of Lesson X