Thunder flashes across the cave entrance...

...displaying its true evil after the party heard so many foul rumors about this place. It's the tomb of the old king, skeletons of past adventurers are hung at the entrance to ward off potential intruders. The four adventurers have been looking for this place for days now and finally Redgar the Ranger finally tracked their way to the entrance. Apparently bandits have been plundering the place and it holds a very powerful artifact that must never be placed in evil hands. The Mayor promised to give a reward of 500 gold coins upon returning of the artifact to him. Cira the Cleric closes her eyes and mutters a prayer, the rain drips
down her metal armour, she kneels in the waterlogged soil and completes the prayer. Snapping open her eyes they glow a green, she nods to herself and says
"Yes, the dead walk here in this tomb, I can see them. We best be careful..."

Warik the wizard nervously pulls back his hood, he glances at the sky a bit before staring at the entrance. "S-s-s-so we're going in there then?" His hands begin to shake as he peers into the darkness.

"Aye lad, let's go!" Redgar pulls out his bow, docks an arrow and carefully stalks into the darkness. Cira follows and gestures for Warik to come. Warik stumbles into the wet mud face first, ruining his newly made robe. He grumbles as he stands up and dusts himself off. He throws his hands in the air, and then cups them near his head. He mutters some words and a glowing orb follows him...he cast a light spell so he can see better.

The party enter the cave, a faint drip of water can be heard in the distance which echos off the walls. Warik sends his orb in to provide light in the area...wrong idea...5 skeletons were waiting for them in the darkness...
Redgar, as gracefully as a cat, draws out his two rapiers and begins to strike at one of the skeletons, it barely does a scratch "My swords are not working!" he bellows. A bright yellow light suddenly bursts into the room, followed by the sounds of singing angels. Two of the skeletons run away in fear whilst one explodes on the spot. Warik nods to Cira "I'm so glad we bought a cleric along", he raises his hands, closes his eyes and mutters some arcane words...3 blue balls of energy appears in his hands in which he directs them to another skeleton. They slam into the monster, throwing him across the room, Warik nervously laughs at his power.
Ok, maybe a bit of an extensive example (not a very good one either!) but this is the sorts of stories you could be telling verbally. It maybe a bit overwhelming to do at first, writing stories and guiding players through it, but it's incredibly easy once you get the hang of it.

But how does one go about doing this?
Easy, just click on the link Writing the adventure to see a mini guide about how to write an adventure.
If you've already written one up, have a glance at Playing the adventure which gives you tips about how to tell the story.
Also, you could check out an aspect of D&D and look at the video about how combat works or setting up your own group.