"He will stand and shepherd his flock in their strength of the Lord, in the majesty of the name of the Lord his God. And they will live securely, for then his greatness will reach to the ends of the earth." NIV translation
This verse tells of the fact that, during the Millennial Reign, the glory of the Lord will be in all the earth. Everyone will know of the Lord because of the fact that He intervened on behalf of His people to save them from the nations. So, what does it mean that He will "shepherd his flock"?
First and foremost, a shepherd spends time with his sheep so that they get used to hearing and responding to his voice. This speaks of the Millennial Reign being a time of learning to listen and know the ways of God. But, it also speaks of the fact that He is shepherding us, as Christians in the world today. During the thousand years, it will be the voice of the King but, for now, we have the voice of God living in us through the power of the Holy Spirit. The second thing is that the shepherd protects the flock from its enemies and, during this time, nobody will threaten His people anymore.