There are several conflicts (both external and internal) in Shakespeare's play Macbeth.
External conflicts, as you may already know, include a character versus another character, society, nature, and factors beyond the character's control.
Macbeth, for example, faces the following external conflicts:
1. Macbeth versus another character: Although Macbeth is in line for the throne (which, unbeknownst to him, would have come to him in due time--without having to take multiple lives), he must eliminate Duncan. However, once Macbeth assumes the throne, he must continue to kill character after character--primarily out of paranoia--to keep his coveted crown.
2. Macbeth versus society: Thou shalt not kill (referring to pre-meditated murder) is a natural law that is a foundation for civil laws world-wide. By committing murder in the first degree, Macbeth is choosing to go against both the natural and civil law, the consequences of which affect and endanger him, Lady Macbeth, and his ill-gotten crown.
3. Macbeth versus forces beyond his control: The biggest force beyond Macbeth's control is the concept of fate. Had Macbeth been patient, the crown would have come to him naturally. By killing Duncan, and engaging in the bloodbath that follows to ensure the crown remains his, and his alone, Macbeth interferes with fate. His consequence for taking matters into his own hands leads to death: Banquo, his best friend, Lady Macbeth, and ultimately, his own death.
Macbeth's internal conflicts include (in order to interfere with fate) his struggle to kill Duncan, who is his kinsman as well as his king, and his struggle to keep the secret of his and Lady Macbeth's roles in Duncan's death.
Macbeth's killing Duncan is hamartia, or the breaking of both a natural law and a civil law that places people other than himself in danger. His consequence for taking matters into his own hands leads to death: Banquo, his best friend, Lady Macbeth, and ultimately, his own death.
By killing Duncan and engaging in the bloodbath that follows to ensure that the crown remains his, and his alone, Macbeth also interferes with fate.
Unfortunately, as Macbeth's story is a tragic one, the resolution (which began with hubris, or false pride) includes Macbeth appearing to have gone insane (in the truest sense), a lack of remorse for his actions--thereby eternally damning his soul to hell--and his death at the hands of Macduff, a possible instrument of fate, righting Macbeth's wrongs.