not till at least series 4
Arthur hasn't YET. Only Lancelot, Gaius, Merlin's mother, Merlin's friend from his old village Will and Merlin himself (obviously) know that Merlin is a sorcerer. Lets keep our fingers crossed that Arthur does find out, If Merlin tells Arthur, imagine Arthur's face, or if Arthur realizes Merlin is a sorcerer and confronts him, imagine Merlin's face!! Added by Queen Arwen: Arthur may not have found out yet, but apparently he will in Season 5. This is from reliable sources, and is not just hearsay!
Stephen Dillane was Merlin in 2004 movie King Arthur.
Arthur doesn't know yet.
he is a wizard from the time of King Arthur. Merlin helped raise King Arthur
Merlin, is a wizard and a great friend of King Arthur.
Merlin was Arthur's tutor when he was a child in the care of Sir Ector. Merlin was the one who brought Arthur to Sir Ector from Arthur's mother Igraine. Merlin is responsible for educating Arthur to be the king he is supposed to be.
merlin the enchanter was the person who raised king arthur and helped him
They met in King Uther's castle and they ended up fighting, Merlin didn't realise that Arthur was the prince.
"who WAS Merlin?'' you talk as if he is dead, for that is impossible for he lives outside of time. but to answer your question, he IS a fabled wizard who has extraordinary powers, who was the long loved advisor of the high king arthur.
Merlin
Morgana in the TV series, Merlin, is said to be King Uther's ward, But really in the legend she is Arthur's evil step sister Morgan La Feye. In the first series there is some suspision into whether Arthur and Morgana fancy/love each other and the same with Merlin! But soon after Arthur is in love with Guinevere which is in the Arturian Legend. So that leaves Merlin but soon after in late Season 3 and 4, She is evil and hates both of them.So, Morgana loves niether Arthur nor Merlin.