Shakespeare's principal source for the story of Coriolanus is a history written by Plutarch, of a Coriolanus who supposedly lived in ancient Rome. Shared with this source material is a concern for the overlap between virtue and valour; whereas, in Rome courage and bravery in war were considered to be virtues, Shakespeare's play is not completely convinced of this equation. Shakespeare deviates from other literature that focuses on heroes by making Coriolanus a flawed man, whose martial excellence does not necessarily translate into goodness of character. The historical Coriolanus of Plutarch was also a flawed character, similar to Shakespeare's Coriolanus in his great military successes, hubris, banishment, and death at the hands of Rome's enemies, whom he was trying to serve.
Although Shakespeare's play follows the basic plot outlines of Coriolanus' story as related in Plutarch, there are a few key differences in Shakespeare's play that add to its timeliness and relevance for the audience. Among these is a change in the motivation for the people's unrest; in the original, the people were stirred to revolt by usury, but in Shakespeare's text, their revolt is motivated by a lack of corn. Just a year before Coriolanus was first performed, there were food shortages throughout England that sparked popular riots by the poor. The people charged the upper classes with hoarding grain, which was also the plebeian charge in Coriolanus; the aristocracy countered, as do their Shakespearean counterparts, that it is bad weather and an overall lack of grain that was to blame. This changed motivation would have been particularly resonant with Shakespeare's audience, as a significant part of their recent history is duplicated exactly in the framework of the play.
Another major departure from Plutarch's text is the depiction of Coriolanus himself, and the society in which he lives. Plutarch's Coriolanus is a man of some political cunning and experience, who was actually a valid political leader, and well regarded by all society for his valor and boldness. Shakespeare's Coriolanus lives in a society where only the patrician class prizes military victory; the mass of the people see little virtue in Coriolanus' skills. Also, Coriolanus is a man who is unable to rule politically, rely on words instead of actions, and control his great temper; on the battlefield, he's an asset, but in society, he is a liability and a loose cannon. Shakespeare's Coriolanus is a man doomed because he is living in the wrong era; military heroes like him are of little use to a peacetime society, and are completely impractical in a society whose greatest challenge is to arrange itself internally, rather than conquer its neighbors.
The political struggle between the common class and the aristocracy is based on events that happened during the life of Coriolanus; during this time, Rome was making a somewhat rocky transition between monarchy and a more republican form of government. But, in addition, this struggle between classes is also reflective of the unrest of the people in England that occurred in the years before this play was written. Also, under King James I, under whose reign this play was written, the absolutist model of government which still ruled England was being called into question. The English Parliament, which had few powers, was beginning to invoke the model of the Roman Republic as a more valid governmental form, and to question the good of monarchy for society. This question, of absolutism vs. republicanism, was key from Shakespeare's time up through the 19th and 20th centuries, when the rights of the British monarch were becoming continually more limited, and the Parliament gaining more and more power over the country.
Questions of social strain between classes were also relevant to Shakespeare's life and career; in 1608, the same year as Coriolanus was written, Shakespeare's company was hired to perform at the Blackfriars theatre rather than the Globe. This not only meant a change in locales, but also a change in audience; whereas at the Globe, plays were viewed by a mixed audience of gentry and commoners, the audience at the Blackfriars was almost exclusively comprised of gentry and aristocrats. This meant that Shakespeare would have to consider any political messages in his plays very carefully, as any sentiments that challenged the monarchy and class system would have meant enraging most, if not all, of Shakespeare's privileged audience. These considerations are especially valid in consideration of a play like Coriolanus, which is not only among Shakespeare's most politically charged work, it was of particular relevance during the time it was written.