EZEKIEL 1:28 
 

As the appearance of the bow that is in the cloud in the day of rain, so was the appearance of the brightness round about. This was the appearance of the likeness of the glory of the LORD. And when I saw it, I fell on my face, and I heard a voice of one that spoke. [AKJV]
 

The appearance of the brilliant light all around Him was like that of a rainbow in a cloud on a rainy day. This was the appearance of the likeness of the glory of the LORD. And when I saw it, I fell facedown and heard a voice speaking. [BSB]

This was not just a metaphor but a real "Rainbow" formed by the Brightness surrounding the Glory of the LORD on the Throne. As it is written,
 

[Revelation 4:2-3] — "And immediately I was in the spirit: and, behold, a Throne was set in heaven, and One sat on the throne. And He that sat was to look on like a Jasper and a Sardine Stone: and there was a Rainbow round about the Throne, in sight like to an Emerald."
 

Rainbow, Lightning and Thunderings, are usually shown to us during cloudy and rainy days. While Rainbow is scarcely seen with every cloudy and rainy storm, the Lightning and Thundering are almost seen and heard with every cloudy and rainy storm. The greatest rain that brought the flood of Noah lasted forty days and nights with Lightnings and Thunderings empowering the rain. But no Rainbow was seen until almost towards the end of the year, before the Rainbow was revealed as token of Covenant between God and the living creatures in the Earth.
 

But behold, the Brilliance or Brightness (Light) of the Glory of God forms and upholds a permanent  "Rainbow"  surrounding Him on the Throne. One of the differences between this Rainbow and that of the other rainbow that visits occasionally during a rainy cloudy day is this: "This Rainbow is a revelation of how the Glory of the LORD looks like" while the other rainbow is a memorial service or reminder about an ancient covenant that forbids the flood of Noah from becoming an affliction that rise up the second time on the earth.
 

Now understand this: the Glory of the LORD is not just consisting of the Brightness, Light, Splendors and Colors of Beauties surrounding Him on the Throne.
 

There are many other things that express the Glory of the LORD. Nevertheless, this Rainbow is illustrating the Glory of God that the Brightness or Light surrounding Him forms. The top Bible verse said that the appearance of the brightness around Him is like the rainbow in cloudy day. And I cited from "Revelation 4" that the brightness around Him is actually Rainbow around Him, in sight like an Emerald or Beryl. This means the Rainbow around Him is like the rainbow we saw in cloudy and rainy day.
 

And the rainbow we saw was a multicolored rays that formed an arc or circle in the sky, perhaps as spectrum that is both a refraction of the Sun's Rays and a reflection of them. I use to know how a bright and white Light rays could be refracted to give all the other basic colors or coloured rays, to prove that all other colors came out of white either by different wavelength or different refraction.
 

The Brightness of the surrounding Light around the LORD is like Rainbow around Him, and this Rainbow is not just about divers Colors but also about divers degrees of His glory one could see with his/her unveiled eyes. The more your eyes are unveiled to see Him clearer, the more brighter it would seem His Glory has grown or increased in degree or  intensity. This does not mean His Glory has changed, but means you the seer has changed by having more veils covering or wrapping your eyes removed for you to see more clearer and lesser of the mirror/glass interface between you and the Rainbow to seeing the Glory and Brilliance of the LORD.
 

Ezekiel fell facedown as soon as he saw the Glory of God in greater degree than that which John, Moses, Daniel, or David saw in their visions and revelations. For Ezekiel saw through Him, saw His full Shape as Man-Like, saw inside the Light or Brightness to actually seeing the Fire burning inside Him like Amber, which none of the others saw and wrote about with details of the Throne, the Firmament, the Rabim/Living Creatures, and the eternal Wheels.
 

Ezekiel fell as soon as he saw Him the much he could, and he began to hear His Voice speaking in his fallen sleep in that vision. Enoch too had similar experience. Daniel and John too had to fall under certain visions, when what they were seeing had drained their strength. Even the twenty four elders keep on falling before Him during intensity worship sessions. Those saints who made it into dwelling in His presence do occasionally fall during their worshiping Him because it takes a lot to keep standing as you delve deeper into His Glory, Awesomeness and Intensity of His indescribability in excellence, perfection and power.
 

This is the best version of Gravity or the law of Gravitation: “Falling while Beholding Him — Both falling in love, falling in worship, and falling in fainting, at Him.”