"Sons of Anarchy" is a television show based on the William Shakespeare play "Hamlet," and therefore each episode of "SOA" shares the same themes as "Hamlet," such as moral corruption, revenge, appearance and reality, and mortality. Jax, the main protagonist, encounters one or more of these themes in each episode.
Jax has to regularly deal with the corruption of his stepfather, Clay, and mother, Gemma. Clay has abandoned the founding principles of the Sons of Anarchy Motorcycle Club to pursue wealth and power, while Gemma has shown disloyalty by marrying Clay so soon after the death of Jax's father.
Revenge factors prominently into "SOA" as well, particularly as Jax seeks to take revenge for the misdeeds of Clay.
The Sons of Anarchy Motorcycle Club itself, in every single episode, provides a stark contrast between appearance and reality. The club appears to be a solid and unified band of brothers committed to a single purpose. In reality, the bonds between club members are exceedingly brittle, and each member acts in pursuit of his own agenda.
Finally, no theme permeates "SOA" more than mortality, as every episode carries with it the specter of dead characters, as well as the potential death of additional important characters.