16 He causes all, both small and great, rich and poor, free and slave, to receive a mark on their right hand or on their foreheads, 17 and that no one may buy or sell except one who has the mark or the name of the beast, or the number of his name. Revelation 13:16 - 17 (NKJV)
The above verses are perhaps some of the most well known, likely even by those who are not Christians. They, in two simple, straightforward, unclimactic sentences, describes what is commonly known as the mark. The description is deceptively simple yet there is a mystery about the mark because they don't actually say what the mark is. I suppose part of the reason is so that it can be unveiled and accepted in away that will allow deception to overshadow it or keep its nature hidden from those who do not read the bible and will ultimately choose to receive it. But here and in just a few other verses elsewhere does the bible give us some awareness of the framework and impact of this, one of the more notable signs of the end times. Understanding the mark and declining it is immensely important. There are two more verses that are critically important to gaining a more complete understanding about the mark.
9 Then a third angel followed them, saying with a loud voice, “If anyone worships the beast and his image, and receives his mark on his forehead or on his hand, 10 he himself shall also drink of the wine of the wrath of God, which is poured out full strength into the cup of His indignation. He shall be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb. 11 And the smoke of their torment ascends forever and ever; and they have no rest day or night, who worship the beast and his image, and whoever receives the mark of his name.” Revelation 14:9 - 11 (NKJV)
20 Then the beast was captured, and with him the false prophet who worked signs in his presence, by which he deceived those who received the mark of the beast and those who worshiped his image. Revelation 19:20 (NKJV)
These verses give additional, grave insight into the hatred God has for the mark and the mark's permenance in the individual who receives it. It plainly states if you recieve the mark you receive the wrath. There is no indication that the mark can be recieved and wrath avoided or that the mark can be received and then removed or undone. They let us know that anyone who recieves the mark will experience God's wrath in full and in hell they will be tormented day and night forever. And those who take it will be deceived in some way about the mark. Deceived could mean the mark itself doesn't come with a neon sign or some clear identifier that it's the mark and people will be decieved in that way, by the lack of certainty that it is the mark. Another way deception might play out is the one promoting it may trick people into believing and trusting in him and along with that trusting this mark that he promotes.
There are many theories about what the mark ultimately will be and many believe it ultimately will be tied to or part of the worship of a man, the beast / the antichrist. Meaning, those who worship him will want to take his mark. It's very possible this is exactly how things will unfold, but I have a different view for a few reasons. I believe there certainly will be those who worship this man and give him their full allegience. That in and of itself is enough to warrant God's wrath. Meaning, someone who worships the beast to that degree with such sincerity has no need of an additional mark to solidify or qualify for God's wrath. They've already earned it through their worship of the antichrist. Antichrist worship is enough on it's own from God's point of view.
It would seem to me, therefore, that the mark is in some way independent of worshiping the beast. Most people seem to think there will only be 2 categories of people in the tribulation, the Ultra Righteous and the Utterly Wicked. I believe there will be a middle group. Take, for example, a non-Christian, but extremly "nice", "innocent" grandmother who's 80 years old. If she's in the tribulation, I don't know that she'd qualify for being utterly wicked and not being a believer would disqualify her from being ultra righteous. So she's somewhere in between. You can probably imagine many other people who would fit a similar description. Would she or they willingly worship the beast with all their heart? Maybe or maybe not. But would she take a mark so that she could buy food to feed herself? That seems more likely. Being able to buy and sell (participate in commerce) seems like an extremely enticing proposition. It therefore is no wonder that it's used as a way to pressure people to receive the mark. Keep in mind, if someone so loves the beast that they worship him there would be no need to lure them into receiving the mark. They'd do it willinginly with no strings attached. The ability to buy and sell is used for those who are uncertain, those who would otherwise not recieve it but do so under distress, fear, and concern over their wellbeing.
But if the bible simply describes the mark as being a way to buy and sell, and it's possible it's independant of worshiping the antichrist, then the pressing question is: what's so bad about the mark? Why is someone doomed to hell because of it? To try to come to an understanding of what that reason might be and why God hates it so vehemently, let's look at some characteristics of the mark as the bible describes it and see if we can link it to another situation the bible described that also incurred God's judgement.
There are two other verses not found in Revelation that I feel are important to understand.
37 But as the days of Noah were, so also will the coming of the Son of Man be. Matthew 24:37 (NKJV)
The Nephilim were on the earth at that time (and also immediately afterward), when those divine beings were having sexual relations with those human women, who gave birth to children for them. These children became the heroes and legendary figures of ancient times. Genesis 6:4 (ISV)
In Matthew 24 Jesus makes reference to the days when he returns being like the "days of Noah". Genesis mentions Nephilim (Giants) being on the earth at the time of the flood - and also after. And it gives no indication it was a local problem to a particular city or town. It was a whole Earth issue. It's been speculated that Jesus may have been alluding to or including the reality of the Nephilim at the time of the flood as a way to give insight what might be going on when he returns. What was going on when the Nephilim were around at the time of the flood? In short, there was a gene problem happening. Man was being currupted as a result of the fallen angels having children with earthly women. The offspring were something other than purely human. They were "giants" and apparently had notable characteristics that made them legendary. Some have speculated that these Nephilim are the basis for many of the mythological traditions around the world. We can't say with any certainty but Hercules, Zeus, and others may have had their origins in actual Nephilim that were on the earth at the time of the flood. The main thing to understand is that genes were pure anymore. And this intermixing of angels and man was not something God condoned and so was at least part of what was judged by the flood.
If we understand that corrupted genes or altered DNA as a result of alien human relations brought about Gods judgement, then when Jesus said the same thing will characterize the time around his return, we are left to wonder if there might be a focus on genes or DNA in some way as we get closer to the end.
It is my personal theory that the mark whatever shape or form it won't necessarily be completely obvious that it is the mark as certain aspects about it will be hidden or not immediately disclosed but later will be revealed. It's possible that it may be described as doing one thing but may at the same time do something else. It's my belief that it will deliver something that will alter, corrupt, or in someway impact human DNA in a way that God opposes and earns the receiver of it perpetual wrath and torment in hell. The mark being associated to some type of DNA profile seems to fit as well since once DNA is corrupted or altered, an individual can do nothing to change that. The DNA change can't be undone. As we seem to be getting closer to what appears to be the end of human history before Jesus returns, it is no wonder to me that DNA, mRNA, and other gene therapy or gene editing related programs seem to be taking center stage, gaining wide public acceptance, and is quickly advancing. Along with that, tracking technologies, serious discussions about placing restrictions on individuals that don't comply with recommendations, and a gradual movement in the direction of heavily encouraging or mandating the receiving of treatments. These all point to something fitting the characterstics of what the bible describes the mark being like taking shape.
It is important to note that simply rejecting the mark is not enough to be saved. You still have to accept Christ. That is truth for all generations.