Money as a symbol of power
When the Vikings land on England's shores, the kings of the Anglo-Saxons are there to meet them and to hear their terms. The Viking lords demand a tribute as a symbol of their subjection to Viking law and to the thrones of the Vikings which are north and east. The Anglo-Saxons demonstrate the symbolism of money by rejecting their command and by taking it as an act of political warfare. Now, because the Vikings have asked the Anglo-Saxons for money as tribute, the two nations are officially at war.
The fight for the king
A common motif in epic poetry is an honor for the throne which transcends a person's personal honor. Lord Byrhtnoth is not about to pay tribute to the Vikings who he feels have no right to be here in the first place, but that does not mean he is his own sovereign. His battle becomes a battle to the death as a loyal servant of his king, King Ethelred. That symbolism is often lost on modern audiences who are not familiar with concepts like loyalty to a throne. The king is a civil servant and a symbol for the nation's just authority. The king is a symbol for Byrhtnoth's attachment to his own land.
Vikings as chaos
The establishment of the Anglo-Saxon society is under threat by warring neighbors to the north who are threatening total domination in the region. This is suitable symbolism for chaos. The Vikings are imposing their authority as a symbol of their timeliness—it is time for them to reign, they feel. But to the English, the changing of the status quo comes with the full symbolism of doom and death. They are not going to stand by and do nothing while their lives crumble around them; they will fight. But who can win a fight against chaos? No one can protect their village forever; so the battle is heroic because they fight in spite of their knowledge that it is a lost fight. It is a suitable symbol for the conservation of tradition which the poetry also accomplishes in its existence.
The water battle
The English realize that their battle would be easier if not for the Vikings establishment on a local isle which they can use as a hub for wide-ranging water-based attacks and invasions. The water is a natural ally of the Vikings who are experts in sea-faring, but also symbolically because they are the force of chaos and water is a natural symbol for chaos. One reason for that is that water is sometimes good, like in a healthy rain, and sometimes bad, like a hailstorm on a field of crops. In this case, they realize that the Vikings are more naturally suited for water sports than they.
The martyrdom motif
Ultimately, martyrdom is heralded as the mark of true heroism. It is very difficult for anyone to accept death, as Godric, son of Odda, proves. Yet, for the heroes who are able to find their severity, their self-control even to the point of death makes them martyrs for their nation, pillars of hope where otherwise the defeat might be permanently crushing. Eventually, when the English more successfully resist the Viking nations, one can be sure that this poetry and its epic quality were cited in those battles. The poetry through this martyrdom motif makes the fall of the Anglo-Saxons into an Alamo situation.
