The theme of friendship and loyalty is seen through the relationship between Hamlet and Horatio. Horatio is the only character that Hamlet can truly trust during the play. He was a student at Wittenburg where Hamlet studied and comes all the way from Germany for the funeral of Hamlet's father. His loyalty and friendship to Hamlet are unquestioned. Even at the beginning of the play, the guards recognize this and Horatio is the one who they turn to when they see the ghost. Horatio is the only person Hamlet trusts to reveal his suspicions about Claudius. Before seeing Claudius' reaction to "The Murder of Gonzago", Hamlet praises his friend. He says,
"For thou hast been
As one, in suff'ring all, that suffers nothing;
A man that Fortune's buffets and rewards
Hast ta'en with equal thanks; and blest are those
Whose blood and judgment are so well commeddled(65)
(Act III, scene ii lines 54-65)
"Give me that man
That is not passion's slave, and I will wear him
In my heart's core, ay, in my heart of heart,
As I do thee."
( Act III, scene ii, Lines 67-69)
Even Claudius trusts Horatio to look after Hamlet after Hamlet's encounter with Laertes at Ophelia's funeral. In the end, Horatio proves to be a very loyal friend when he is willing to die alongside Hamlet. However, Hamlet has a better plan for him. He asks Horatio to tell his story and thus preserve the lessons of his life for posterity. So Horatio agrees and becomes the perfect example of a loyal friend.
Sorry, My post (above) seems to have gone hay-wire! And it was long and brilliant too! Oh well.
In a nutshell... The most important example of loyalty is Hamlet's Mother's lack of loyalty to Hamlet's Father. While Hamlet has barely even begun to greive for his dead father, his mother has buried him, remarried and now cheerfully shows all the signs of a sexually busy 'blushing young bride'. Hamlet rages at this. Her disloyalty is incomprehensible to him. Her betrayal is worse than his father's death. On Hamlet's long list of troubles, his mother's betrayal is at the top, by a long way.
This is the very heart of the play.
Consider this... when Hamlet finally confronts Gertrude about her re-marriage, he is so angry and so bursting to tell her what he thinks about it, that when he murders Polonius, his first line in response to having mistakenly killed someone is basically, "Yeah ok, that's not good, but at least I didn't BETRAY my FATHER!" and he immediately returns to demanding his mother explains her disloyalty, while forgotten Polonius's warm life-blood pools on the floor behind him.
There are many examples of loaylty in Hamlet. But the most important is