What is the story of the Companions of the Cave, and what is the merit of Surat Al-Kahf?

Surat Al-Kahf is a Meccan surah, with 110 verses. It contains four stories: the People of the Cave, the owner of the two gardens, Moses and Al-Khidr, and Dhul-Qarnayn. There are Hadiths from the Prophet (peace be upon him) regarding its virtues, among them: "Whoever memorizes ten verses from the beginning of Surat Al-Kahf will be protected from the Dajjal (Antichrist)." And whoever encounters the Dajjal should recite the opening verses of Surat Al-Kahf to him.

As for the story of the People of the Cave, they were youths who fled with their religion from a polytheistic king. So, they sought refuge in a cave and slept for three hundred and nine years, during which Allah preserved them by turning them from side to side. When they awoke, they sent one of them to buy food, and they discovered that time had changed. In the story there are signs and lessons, among them: whoever seeks refuge with Allah, He will shelter him; an encouragement to pursue beneficial knowledge; gentleness and caution against temptations; a demonstration of these youths' desire for religion; and that the people among whom they were resurrected honored them and resolved to build a mosque over their cave. The story also indicates the prohibition of excessive delving into unimportant matters and asking those who lack knowledge.