Summary: The Bible tells us that there will be a time when some will "depart" from the "faith"
Whenever there is a cataclysmic event, like a global pandemic, a new political administration, fires, floods, earthquakes, etc., etc., etc., the cry goes out that it may be the end of days and you need to get your act together so you don't miss the 'Rapture' or take the mark of the Beast (Rev 16:2, 19:20), which is currently conjectured to be a computer chip inserted in your hand or forehead.
Back in the '70s and '80s, thanks to such books as the "Late Great Planet Earth" by Hal Lindsay, and the 'Left Behind" series of books by Tim Lahaye and Jerry B Jenkins, the dominant belief was that a Pre-Tribulation Rapture would take place. I remember a book, written by a NASA engineer, that was published on January 1st, 1988 called "88 Reasons Why The Rapture Will Take Place In 1988." When it didn't happen, he published another book called "The Final Shout: Rapture Report 1989," which was essentially an '89 Reasons Why...' book.
Today, it is rare to even hear about the 'Rapture' in church, most likely because 'prophecy experts' have given specific dates for the return of Jesus, that have come and gone like the ways of the Dinosaur over the years. There are basically four camps people fall into about the Rapture: No-Trib, Pre-Trib, Mid-Trib, or Post-Trib, which was the dominant belief in the church up until the 20th century. Personally, I'm Pan-Trib as I wait to see how it will all pan out!
The Bible tells us that there will be a time when some will "depart" from the "faith" "by devoting themselves to deceitful spirits and teachings of demons" (1 Tim 4:1 ESV, also 2 Tim 3:1-5). The word 'depart' is the Greek word "aphistemi" which is where the word 'apostasy' comes from. It means to actively instigate to revolt, desist, desert, defect, etc. It is far different than a person who is simply ignorant or naïve of the Scriptures and unknowingly espousing heresy.
The Bible also says that it is "impossible" for " 'those who fall away" to "renew them again unto repentance, seeing they crucify to themselves the Son of God afresh, and put him to an open shame" (Heb 6:6 ESV). Those who 'fall away' and "go on sinning deliberately after receiving the knowledge of the truth," "there no longer remains a sacrifice for sins, but a fearful expectation of judgment, and a fury of fire that will consume the adversaries" because they have "trampled underfoot the Son of God, and has profaned the blood of the covenant by which he was sanctified, and has outraged the Spirit of grace" (Heb 10:26-30 ESV). This is an irredeemable willful act of defiance and rejection of Jesus as Lord and Savior. These people are a "bad tree" that only produces "bad fruit" and were never Born-Again because Jesus never knew them, otherwise they would have continued with Him (Heb 6:4-6,27,10:26; Matt 7:16, 13:1-9, 18-23; Rom 8:13;1 John 2:19, 3:7-10).
Jesus taught the Disciples, before the day of Pentecost when the new dispensation of salvation by grace began, the "world" would hate and persecute them as they hated and persecuted Him "without a cause," because they are "not of the world" (John 15:18-25 ESV). Jesus reminds them that when the "Helper" comes on that day, who is the "Spirit of truth, he will bear witness about me. And you also will bear witness, because you have been with me from the beginning" (John 15:26-27 ESV). Jesus then said to them, "I have said all these things to you to keep you from falling away" (John 16:1 ESV).
The words "falling away" is a translation of the Greek word "skandalalizo" which means to entice to sin, to trip up, to entrap, to scandalize, and is where we get the word 'scandal.' Jesus promised that if His disciples understood what it means to be a genuine disciple they would not be scandalized when persecuted.
Mark of the Beast
There will come a time when people will make the reprehensible and blasphemous act of willful defiance against God by taking the Mark of the Beast, which is essentially worshipping satan (Rev 13:15-16). The word “mark” in Greek is 'charágmatos,' and comes from the word ‘charássœ,’ which means to carve; to engrave or sculpture something; an impression, inscription, or an etched, carved, branded, mark or symbol, as on an animal, coin, statue, or false idol (See Acts 17:29).
In antiquity, a “mark” was branded for stigmatization on the right hand or the forehead of people, such as slaves, to show others they were their master's property, as well as upon those who were willingly branded in a temple with the symbol of their deity.
In Islam, the mark of the Beast (aka Bismillah) is also a line drawn on the forehead and must be worn on the right arm/hand of every Muslim at Judgment, and is what distinguishes them from non-believers (Tirmuthi 2369).