William Shakespeare has had the greatest influence, most significantly, on the English language. One of the reasons why his plays, sonnets and his name remain synonymous with the study of English for scholars from about the age of eleven or twelve is because he is credited with having coined many words and phrases in use today and his plays are consistently acted, revised and re-shown. He has contributed to the structure of sentences and language and his style has been emulated by many other famous writers and poets such as Charles Dickens who wrote Oliver Twist, David Copperfield and A Christmas Carol to name only a few. In Dickens's Nicholas Nickleby, Mrs Wititterly comments that, "Shakespeare is such a delicious creature."
As far as recent authors are concerned, even Ray Bradbury took some inspiration from Shakespeare in his novel, "Something Wicked This Way Comes," which is a line taken directly from Macbeth, Act IV, scene i, line 45 when the three witches see Macbeth approaching, as he comes to seek their advice and they convince him that, "Macbeth shall never vanquished be..." (line 92). Bradbury's novel is about the fight between the forces of good and evil and, as in Shakespeare's Macbeth, some people are more influenced by evil than others and circumstances and opportunity play a large role. It seems that the themes that Shakespeare wrote about more than four hundred years ago have not changed.
Shakespeare wrote about tragedy, comedy and history and his plays and sonnets often utilize iambic pentameter (da DUM da DUM) which, amongst his other style uses, appears in, for example, Macbeth, Act I, scene vii, lines 81-82, when Macbeth is steeling himself to murder Duncan and he says, "Away, and mock the time with fairest show; False face must hide what the false heart doth know." Shakespeare's ability to create drama and intensity, not only from his words but from the rhythm, add to his recognized prowess. Although, Shakespeare was not the first to use iambic pentameter, the style is very popular, perhaps due to his huge popularity. He, with other actor friends, established the original Globe Theater in London in 1599 which, although the original burned down, contributed to a society which appreciated and preserved his works.
In terms of Macbeth itself, Shakespeare used names and distant historical events and his version of Macbeth was designed to please his king (James I) and was never intended to be an historical account of the real Macbeth from the eleventh century.
Shakespeare has then contributed and, perhaps "changed" history because the way we communicate in English is influenced by him and, although students may disagree when they are studying Shakespeare and are somewhat confused by his plays, Shakespeare simplified English, allowing others to emulate his style and themselves become famous writers and poets; something that may otherwise have been impossible without his effect on their work.
Shakespeare's Macbeth was written within weeks of the coronation of James VI of Scotland becoming James I of England. Then, in 1603 Shakespeare's company of actors was named "The King's Men"; therefore, in return for this honor, the actors were expected to play at court whenever required. This contract afforded the King's Men between ten and twenty performances a year for the remainder of Shakespeare's career. So, Shakespeare strongly wished to remain in the king's favor.
Whereas records from the Holinshed's Chronicles reveal that Banquo was an accomplice to Macbeth in the slaying of the king, since King James was a descendant of Banquo, in writing Macbeth, Shakespeare may have changed Banquo's character to avoid having the king's ancestor as a murderer. Also, King James believed strongly in witches, so Macbeth is visited by them in his play. Further, to make Banquo and his descendants appear more favorably in the play, Macbeth becomes a villain when in reality Duncan was said to be reckless and greatly disliked while Macbeth was favored by the people and reigned successfully for seventeen years.