Christ IS King. For this He was born and for this He came into the world (Jn 18:37). Amongst the saints and angels in heaven, He already rules as the King of kings and the Lord of lords. Meanwhile, amongst us who are still drudging through this valley of tears, His "hour" has not yet come. Fortunately for us – poor banished children of Eve – we do not have to wait until the end of time to get a glimpse of that "Kingdom that will have no end". Our good King has granted that during the celebration of each Holy Mass, his "hour" IS brought forward. He who is already King amongst the saints and angels in heaven, enters our "not yet" as St. John described it in the account of the wedding feast at Cana (Jn 2:1-12).
The hour of the Lord has not yet come; all that must happen is not yet fulfilled, but at Mary's – the Church's – request Jesus does give the new wine now and already bestows in advance, the gift of his hour.
— Joseph Cardinal Ratzinger, A New Song for the Lord; In the Presence of the Angels
The liturgy is not something that we create. It is a gift from the Risen Lord. It is a perennial banquet that is already before us. To attend Mass is to enter into the liturgy of the heavens that has always been taking place. Earthly liturgy is liturgy because (and only because) it joins what is already in process – the greater reality, aka, the Heavenly Liturgy. And whenever He comes, the Risen Lord does not come alone. In the images of the Heavenly Liturgy given to us in the last book of the Bible, He is surrounded by the four living creatures, the twenty-four elders, the multitude of saints and above all, by a host of singing angels.
[…] it is not the case that you think something up and then sing it. Instead, the song comes to you from the angels and you have to lift up your heart so that it may be in tune with the music coming to it.
— St. Benedict of Nursia, The Rule; The Discipline of Singing the Psalms
The Kingship of Christ comes closer to us every time the Sacrifice of the Mass is celebrated in a dignified and worthy manner. Every time we attentively take part in the Holy Mass, we are telling him; Maranatha – Come Lord Jesus! Every time we participate fully and consciously in the celebration of the Holy Mass, we are entering The Ultimate Universe, or rather, the Ultimate Universe gets a chance to break into our cramped and limited multiverses. Every time we kneel devoutly in front of the Eucharistic Lord (for example, when he is raised up during the consecration), we are telling Him, with or without words; Regnare Christum Volumus – We want Christ to reign!
If in word and in deed, we genuinely want his Kingdom to come, we cannot (for example), afford to be missing Mass on Sundays. If we really hunger and thirst for the coming of The Kingdom, how can we not hunger and thirst to receive such an Admirable King frequently in intimate Communion? Which better way to fulfil the, 'Thy Kingdom come' petition of the Our Father and the 'His Kingdom will have no end' prophecy of The Creed, than to participate, digne, attente ac devote, in the Holy Sacrifice of the Altar?
Our King is not satisfied to only come during each celebration of the Mass (which is already A LOT); he also desires to stay with us after the celebration. He especially loves to reside in our spiritual faculties; namely, our intellects, our wills and our hearts …
He is said to reign in the minds of men, both by reason of the keenness of his intellect and the extent of his knowledge, and also because he is the Truth itself and it is from Him that truth must be obediently received by all mankind. He reigns too in the wills of men, for in Him the human will was perfectly and entirely obedient to the Holy Will of God, and further by his grace and inspiration he so subjects our free will as to incite us to the most noble endeavours. He is king of our hearts too, by reason of his charity which surpasseth all knowledge, and His mercy and kindness which draw all men to Him; for there never was, nor ever will be a man loved so much and so universally as Jesus Christ.
— Pope Pius XI, Quas Primas
All power in heaven and on earth has been given to this humblest of Kings (Matt 28:18). We invoke His supreme humility in every Holy Mass by referring to Him as The Lamb of God – the slain yet Living Lamb in the book of Revelation who, thanks to His sacrifice, becomes worthy to receive power and riches and wisdom and strength and glory and honour and blessing (Rev 5:12). He is King even of the reprobates and the damned who, despite themselves, crown him King. They mockingly crown him with thorns, but they crown him nonetheless. They too, despite themselves, fulfil the words of Sacred Scripture that say; Every knee shall bow and every tongue confess, that Jesus Christ is Lord. (Is 45:23, Ps 72:11, Phil 2:10-11, Rom 14:11).
We were born for royalty and we are destined for it. We should live our lives like watchmen waiting for daybreak – constantly looking towards the horizon for the Return of the King.