I have posted on this topic twice before but I have made this new post (composed mostly of what I had written before) to answer a question on another forum, so I thought I would put a copy of it here.
The Lake of Fire (LOF) is mentioned five times in the book of Revelation ..... Rev. 14 : 10 - 11; 19 : 20; 20 : 10; 20 : 13 - 15; and 21 : 8.
Many people have very firm views on what the LOF could be. But since Revelation is so full of symbols, what the LOF stands for will always be open to conjecture, depending on your view of God, as much as anything else.
Those who view God as a vengeful judge see the LOF as a place of horrible physical torment in flames of fire that last for ever and ever. Properly translated, "for ever and ever" really should be "for the ages of the ages", but that doesn't alter the ugliness of this view very much. I personally can't see how people are comfortable worshipping a God who has such horrible intentions for the majority of His creation.
Those who view God with a bit more mercy than that see the LOF as a place where people are annihilated and removed from existence rather than tormented.
Those who view God as a loving Father and the Saviour of the world see the LOF as the place where those whose names are not in the Book of Life are purified and made ready to move into eternity in fellowship with God.
Using this last view, I see the LOF as a reformatory for the rebellious children of God.
Looking at the last reference from above, we see that John gives a definition of the LOF. Revelation 21 : 8 says that the LOF is "the lake that burns with fire and sulphur."
The 'fire' is a symbol representing purification or cleansing or changing of form. Chemically, fire never destroys, it only changes the nature or form of things. Wood burning in a lounge fire is never destroyed but is changed or converted to other substances like smoke, char, ash, heat, light, etc. So fire in the LOF is a symbol for change or conversion of one form or nature into another - the reforming process of the reformatory.
The 'lake' indicates the size of the operation - not a small fireplace, or a forge or even a commercial furnace, but a huge expanse of conversion.
The 'sulphur' adds information about the character of the fire. The Greek word that we translate as sulphur or brimstone is "theion", which is probably the neuter form of "theios" that means divinity. The verb derived from "theion" is "theioo" which means "to make divine."
Putting all these together paints a picture of the LOF being a large scale purifying or reforming process that produces character of a divine nature.
A story which has appeared on the internet over the years in various forms gives me some insight into how this might work.
I love this story as it helps me appreciate one of God's methods of making us Christ-like in our process of sanctification and also helps me understand the references to fire and brimstone and God's purpose in using these cleansing agents.
While reading Malachi 3, a group of women in a Bible Study were struck by the reference to God sitting as a refiner and purifier of silver. To gain a better understanding of this verse, one of the women offered to visit a silversmith, watch him at work, and report back to the group on her observations the following week.
She called a silversmith and made an appointment to watch him work, but didn't mention anything about the reason for her interest beyond her curiosity about the process of refining silver.
As she watched the silversmith, he held a piece of silver over the fire and let it heat up. He explained that in refining silver, he needed to hold the silver in the middle of the fire where the flames were hottest in order to burn away all the impurities.
She asked the silversmith if it was true that he had to sit there in front of the fire the whole time the silver was being refined. The man answered that yes, not only must he sit there holding the silver, but he also had to keep his eyes on the silver the entire time it was in the fire. If the silver was left in the fire a moment too long, it would be injured in some way.
The woman thought about God holding us in such a hot spot sometimes, and began to see the purifying purpose in these experiences under the watchful eye of the Master Silversmith.
The woman remained silent while she let these thoughts run their course, then asked the silversmith, “How do you know when the silver is fully refined?” He smiled at her and answered, ‘Oh, that’s easy — it is fully refined when I can see my image in it.
We were made in God's image originally, and we need to be reformed into that image for fellowship with Him in eternity. He does this in His saints now through the sanctifying work of His Holy Spirit, and in the rebellious through His judgements at the Great White Throne and through the purifying process in the LOF.
I think this story perfectly describes the purpose of the LOF. It is for purifying those whose names are not in the Book of Life and have not had their lives changed by the purifying work of the Holy Spirit during their earthly faith walk.
Different pieces of silver will obviously take different amounts of time in the flame to be purified, depending on how 'unpurified' they were when they were placed there, but eventually the LOF will no longer be needed.
Interestingly, the last part of Revelation 21 : 8 says that the LOF is the second death. It is the death of all that offends God and that needs to be removed from those who have not had the sanctifying work of the Holy Spirit involved in their lives as we've had. But when the LOF has finally finished its work it will no longer be needed and will be destroyed as Paul promised in 1 Cor 15 : 26.