The Captain explains that Macbeth decapitated the enemy and placed it on the battlefield to act as a warning; this could be seen as foreshadowing Macbeth's death later on.
Lady Macbeth questions Macbeth's masculinity and he replies by exclaiming that he is the personification of masculinity. He is offended by her question.
Macbeth recognises that what he sees will be fatal. There is a double meaning here; not only is it a dagger that will cause harm, it could also be a symbol of Macbeth's downfall
Macbeth is angry at the Witches for giving him an empty promise - he doesn't think anything will come of him becoming king if his children can't also be royalty.
Macbeth doesn't want to let LM in on his plan to kill Banquo. Note how his language has changed from "dearest partner" to "dear wife" to "dearest chuck" showing his changing perception of her.