Isaiah 25:6. “And in this mountain shall the Lord of hosts make unto all people a feast of fat things, a feast of wines on the lees, of fat things full of marrow, of wines on the lees well refined.”
In this mountain refers to Mount Zion. Again, this entire chapter is describing events of the Millenial Kingdom, which includes the celebration of the physical return of Messiah.
A feast of fat things could also be translated as a feast of good things. There has been horrible desolation all over the earth under Antichrist, and now peace and order have been restored. Feasts always took place as a time of celebration of victories in war. This one is the ultimate feast, because it includes the presence of Messiah, Who has triumphed over Antichrist and the terrible ones under his leadership, the nations who warred against Israel, as well as His triumph over Satan and his demons.
Wines on the lees: Wine that has been kept for a long time, and the dregs mixed with it to make it strong. It is purified by straining it through cloth, leaving nothing but the pure wine.
Fat things full of marrow is an expression denoting sumptuous entertainment and abundant provisions.