The ideal relationship between king and thane or between lord and warriors is known as "Comitatus." This is a sworn bond to protect the lands the thane inhabits and to protect the king when his kingdom is threatened. If the king demands, the thane must lay down his life it this defense. If the king is killed, the thane is obligated to enact revenge.
The king, in turn, is bound to provide protection for his thanes, to share in the wealth when there is a boon, and to parcel out his fiefdom in accordance of reputation.
It's a symbiosis that comes full circle in Beowulf. Beowulf comes to Hrothgar's defense early in the poem, and other thanes come to Beowulf's late. What the monks who edited the poem over the years seem to be saying, by way of Christian allusions, is that "Comitatus" leads to constant revenge and blood feuds.
The Beowulf poet provides us with the picture of the ideal warrior king in his description of Scyld Sheaf-child in the poem's opening lines:
Often Scyld Sheaf-child [or Sheaf-son] scattered his enemies,/captured their mead benches and brought his enemies low/. . . all those peoples around his borders/over the whale-road had to obey him,/pay him tribute. Now, that was a good king! (ll. 4-11)
In the warrior societies of Scandinavia and Anglo-Saxon England, the relationship between a leader and his warriors is founded on the leader's ability to create wealth, which is then distributed among his warriors and creates a loyalty based on strength and generosity. The key to this relationship is encapsulated in the phrase "pay him tribute" above--in other words, Scyld inspires such fear in other tribes that they are willing to pay him to leave them alone. This tribute then becomes the mechanism by which the bond between Scyld and his warriors is sealed. This relationship--based on power and money or land--is the precursor of feudalism in the Middle Ages.
When Hrothgar and his mead-hall, Heorot, are first described, the poet describes more fully how the relationship between a warrior-king and his people is created and made permanent:
. . . and there within [that is, in Heorot] [Hrothgar] gave away anything/to young and old, as God had given to him,/but common lands or the lives of people. (ll. 71-73)
As a good leader, obviously successful in war, Hrothgar distributes his wealth to "both young and old," thereby creating a relationship between himself and all his subjects, not just his group of warriors. The poet also tells us that Hrothgar gave away neither common land, which means land used by the whole tribe, nor "the lives of people," perhaps an indication that Hrothgar did not consider those whom he had captured in war to be property. Because the Beowulf poet is most likely a Christian monk writing in the 7th or 8th centuries, he is careful to depict Hrothgar as a king who did not traffic in slaves. We know that slaves, often those who were captured in battle, were a valuable commodity in these societies.
At its most fundamental level, then, the relationship between a warrior-king and his warriors is based on the leader's power, his ability to inspire fear in his opponents, and his generosity to his warriors and, more widely, to his people. Wealth and power are the goals in a warrior society, and all relationships are founded on the ability to obtain wealth and distribute that wealth freely to those upon whom a leader must rely to obtain more wealth or land or, in rare cases, a lasting peace, as Beowulf did for the Geats.