You can see the King of Cups as a man with the following qualities or, if the the question concerns a woman, as the male part of her psyche. But I tend to reading the kings as the outward side of a person (job, typical ways of acting, the way the life is led...), no matter whether this person is male or female.
The King of Cups is a sensitive, intuitiv, warm-hearted, feeling man who typically works as an artist, doctor, therapist, healer, mediator or similar. He is always ready to help and to care for others, and he is looking for wisdom and spiritual fulfilment. If you meet a person like this you should make sure, though, that these characteristics are true and not just pretended to seduce or manipulate you.