To be a knight in the Middle Ages, a man needed to possess the following virtues:
* Mercy (Towards the poor and oppressed. They were supposed to be harsh with evil-doers.)
* Fear of God
* Utmost graciousness and courtesy to ladies
I will also add that the ideal knight was gentle, kind, patient, and tender with the poor; with those less fortunate than himself; and with the elderly, women, and children. He learned to be civil, refined, genteel, and temperate. He could be counted on to deal justly and fairly with everyone-the people of his kingdom as well as his fellow knights. A knight was usually selfless and put the safety of others ahead of his own; he was usually physically strong and hardy. A great deal of self control went into being a knight.
It's interesting to note that many of the qualities of a medieval knight are qualities that can still be found today in members of our armed forces.
The first important distinction we need to make here is between real knights and the knight as a literary figure. In reality, a knight is the lowest rank of the nobility, allowing its holder the title of "Sir." Under the feudal system, a knight was granted the use of land in return for providing service to his feudal superior, usually in the form of military service as a mounted warrior, although he might be able to supply money or armed men (his own peasants) in lieu of fighting himself. Much of the model for European knighthood is based on the Roman class of the Equites, the lowest class of Roman nobles, named because they were wealthy enough to supply their own horses when called up for military service, but not members of the Senatorial elite.
The literary and cultural traditions of chivalry and chivalric romance created a behavioral ideal for knights which was quite different from the more pragmatic requirements of possessing wealth and the ability to maintain local order and kill people on command. If we look at the codes of chivalry, they essentially form an ideology designed for use in the training of young nobles in the hope that they will internalize values and modes of conduct beneficial rather than harmful to their societies. This was especially important in the middle ages, when local lords and kings were engaged in power struggles over centralization versus autonomy (reflected, e.g. in the Magna Carta), much in the way that warlords and central governments in Afghanistan, Iraq, Libya, and Yemen are now struggling with one another.
In chivalric romance, a knight was expected to be devoted to a lady (generally one who was either single or married to someone else), be courteous and polite, help widows, the elderly and children, support the Christian faith, and fight according to a detailed code of conduct. Much of the literary tradition of the knight, especially in popular culture, descends from Arthurian romance, the tales of King Arthur and his circle. Even in the late Middle Ages and early Renaissance, though, as is shown in works such as Orlando Furioso and Don Quixote, people distinguished between the literary ideals of knighthood and the messier (and funnier) realities.