There are multiple connections to the modern world one could make when examining William Shakespeare's tragic play Macbeth.
Macbeth's growing ambition came about from his taste of power. This "taste" fueled his ambitious nature. Society today is impacted by ambitious people. While some may not allow their ambition to lead them to murder, ambition is not an idea which died with Shakespeare.
Once Macbeth was in power, he did not want to lose it. This is an idea seen apparent in today's society. Not only do people desire power, they have done things to insure that they keep their power. While not all people go tho the lengths Macbeth did in the play to keep his power, some people do. We have seen many leaders fall, or stay in power, based upon their desire to keep it.
The "war" depicted at the end of the play (Malcolm/Macduff and their armies against Macbeth) is still real today. Our world has been at war, in one way or another, since the beginning of time. As humans, we can accept that there will always be those who believe that they should have power and will declare war in the name of it.