Metaphysical implications -Parmenides

One last time, (I hope) I would love some help.
Here it goes, I know that Parmenides conjectured theorum is For all X , X exists is true.

My question is what are the metaphysical implications of the theorem and the four corollaries?

Short and sweet- I get that metaphysical is about what exists, bit once again this question has me running in circles.

Thank you in advance-