What John experienced on the island of Patmos in Revelation chapter 1 was – quite literary – out of this world. It was off the charts.
When John beheld Christ, he could not find words in his vocabulary – or the vocabulary of any language for that matter – precisely because it did not compare to anything he knew or had ever experienced in the natural before. He was lost for words to describe what he encountered. So he defaulted to what he knew and was universally known to describe what he beheld.
All John could do to describe what he saw was find the nearest and closest comparisons he could think of in the natural realm. There was nothing in the natural and in human experience (and, by extension, in human vocabulary too) that could adequately describe and relate the glory that John was experiencing in that moment. Every aspect and feature of the glory he beheld could only be remotely described employing a simile because it was of a different kind, of a different nature and out of this world.
(Simile: a figure of speech involving the comparison of one thing with another thing of a different kind, used to make a description more emphatic or vivid).
So John did his best with describing what stood in front of him and proceeded in his description in Revelation 1:13 – 16 as follows…
The hairs of his head were white, like white wool, like snow.
His eyes were like a flame of fire,
his feet were like burnished bronze, refined in a furnace, and
his voice was like the roar of many waters.
…his face was like the sun shining in full strength.
John employed multiple similes in order to describe the glory he beheld. But even then, these were just attempts at describing the indescribable and could never do justice to who stood before him.
As John encountered Christ in His majestic glory all he could do in response, the only response he could muster or give, was not to put pen to paper to describe Him to us. Rather, it was, to fall at His feet as though dead.

When I saw him, I fell at his feet as though dead.
Revelation 1:17
It was a very natural and unforced response to the glorious Christ.
John could not do otherwise.
He was smitten by the magnitude of the glory he was faced with.
He could not remain standing in the presence of it.
His knees buckled and gave in.
He capitulated to it.
He was undone by it.
There was no other response befitting the glory that stood before him.
The sheer force and intensity of the presence of Christ in His glory overwhelmed and overpowered him to the point of falling at His feet as though dead.
The beauty, glory and majesty that he found himself in the presence of, totally and comprehensively overpowered him.
His response is probably the more telling description of the glory he beheld.
How do you respond to the revelation of the person and majesty of Christ – in whatever measure – in your life?