Melchizedek, the King of Salem in The Alchemist is a mystical figure who Santiago, the shepherd boy, meets on his journey while traveling with his sheep.
When Santiago meets the king, he thinks he is just an old man. The shepherd boy is slightly preoccupied with what an old gypsy woman has told him about a recurring dream he has had. In this frame of mind, Santiago thinks the man is unimportant. When the old man asks about the book Santiago is reading, the man proves to be very knowledgeable not just because he can read, which the boy had first doubted, but that he has read the book already and has a low opinion of it. The man tells Santiago that he is a king, which the boy doubts at first; however, once he is convinced, he is in awe of the king and listens carefully to what Melchizedek has to say.
Melchizedek is very wise. He knows a great deal about life and what can bring a person personal happiness and fulfillment.
The old king is rather mystical as well. He not only knows things about Santiago that he could not possibly know, but he also can read the boy's mind.
Last, Melchizedek he is slightly prideful. He is not filled with self-importance. After the boy leaves, when the king talks to the Lord (God?), he is humble and honest about himself. He admits that he is giving into vanity, but wishes that after the boy left that Santiago might remember the old king.
Melchizedek is a man aware of the characteristics of human nature. He is patient and non-judgmental. He is also kind in that he fervently hopes that Santiago will be successful in his journey.