One of the major functions of the restored gospel is to prepare us to receive the blessing of the Abrahamic covenant. Elder Russell M. Nelson taught this:
Many of you have already qualified for endowment in the temple, and others will have that great privilege yet in the future. In the temple, with the authority of the sealing power, blessings of the Abrahamic covenant will be conferred. There, we may truly become heirs to all the blessings of Abraham, Isaac, and Jacob.
Russell M. Nelson, Perfection Pending, and Other Favorite Discourses , p.206
One of the major functions of sacred sites is to administer the Abrahamic covenant. There are many aspects to the Abrahamic covenant including receiving the priesthood. However, there are two major components to the covenant - 1. a land of inheritance forever and 2. posterity as numerous as the dust of the earth (see Genesis 13:15-16). Number one is an intimation that man will become like his maker with the eternal power to create life (D&C 132:29-33). Number two is an adumbration that the earth is going to become a Celestial Kingdom (D&C 88:17-20).
These are sometimes referred to as the promises made to the fathers. So, sacred sites not only help us to conform to the image of the Son but also to become heirs of the promises made to Abraham, Isaac, and Jacob. These are promises that make us like our God so that we may inherit the earth as it becomes a Celestial Kingdom. Ultimately we truly have posterity as numerous as the dust of the earth and a land of inheritance forever as promised to Abraham.