The theme of friendship might not jump right out at you, but we think it’s a really important current running through "The Cremation of Sam McGee." Sometimes the speaker seems frustrated by Sam, or angry at the position Sam has put him in. Still, we think he’s also motivated by a real sense of caring and friendship. He feels a sense of duty, of course, but we think he also just likes Sam (or did until he kicked the bucket) and wants to do what’s right for him.
Even after Sam dies, we see the bond between Sam and the speaker continue to deepen and change, which proves the central importance of their friendship.
The friendship between Sam and the speaker is a minor force in the poem. The speaker is primarily motivated by his own sense of duty and honor, rather than friendship.