I don't recall reading this passage of Matthew 13 before that was covered in church last night, possibly because it's at the end of a long line of more-evocative parables-
47 “Once again, the kingdom of heaven is like a net that was let down into the lake and caught all kinds of fish. 48 When it was full, the fishermen pulled it up on the shore. Then they sat down and collected the good fish in baskets, but threw the bad away. 49 This is how it will be at the end of the age. The angels will come and separate the wicked from the righteous 50 and throw them into the blazing furnace, where there will be weeping and gnashing of teeth.
It's definitely not a universalist message, unless the blazing furnace is more of a broiler (or salamander, as I've seen them called on cooking shows) designed for a purgatory-like searing away of shortcomings. Using the salamander metaphor for that would lean more to eternity's smoking section, especially with the weeping and gnashing of teeth; no wailing on this one?
This can be played up as a scare-tactic for preachers, pointing out that not everyone will be in the number when the saints come marching in. That can lead the folks into the pews to wonder if they are going to make the grade or not.
As far as I know, the entrance exam for Heaven is on a pass-fail basis and accepting Jesus and following Him (some better than others) is a passing grade. That leaves the passage as a pointer that there are some trash fish in the nets that ain't worth eatin'.
It's an odd metaphor, to see being sold at market is better than being chucked back into the water as trash, but it is a reminder that God does do some eternal screening. I almost said "eternal triage" but that is our job, to reach the reachable before they turn into those trash fish; there will be some that won't make it, but (at least if we avoid a hard-Calvinist take) there's hope for everyone while they're still life left.