I think it is a metaphor for the path we must take. We all must descend before we can dwell with God. I do not think the messenger was a false messenger. Did he delivery a false message to Lehi?
21 And I saw numberless concourses of people, many of whom were pressing forward, that they might obtain the path which led unto the tree by which I stood.
22 And it came to pass that they did come forth, and commence in the path which led to the tree.
23 And it came to pass that there arose a mist of darkness; yea, even an exceedingly great mist of darkness, insomuch that they who had commenced in the path did lose their way, that they wandered off and were lost.
24 And it came to pass that I beheld others pressing forward, and they came forth and caught hold of the end of the rod of iron; and they did press forward through the mist of darkness, clinging to the rod of iron, even until they did come forth and partake of the fruit of the tree.
The path is through the mists of darkness. It cannot be avoided. It is by clinging to the iron rod that the path is safely traversed. The place that looks safe is the great and spacious building.
The word of God can also be interpreted to mean Jesus Christ himself.
1 In the beginning was the Word, and the Word was with God, and the Word was God.
14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
15 ¶John bare witness of him, and cried, saying, This was he of whom I spake, He that cometh after me is preferred before me: for he was before me.
It is by praying that Lehi is delivered from the darkness. He reaches out for the iron rod. That rod is God or God manifest in the flesh who is Jesus Christ. This story is key to our salvation. We all must pass through the mist of darkness, if we are to gain the tree of life.
They must find it difficult, those who have taken authority as truth, rather than truth as authority.