What is motif? How does William Shakespeare use loyalty as motif throughout Julius Cesar?

A motif is any any recurring element that has symbolic significance in a story or novel

A motif is a reoccurring theme. Julius Caesar revolves around this entire notion of loyalty.

Explanation:

for example, the loyalty of Antony and Octavius is portrayed by avenging Caesars death, and the loyalty from Brutus towards Rome is shown rather than their loyalty to Caesar.