King Duncan goes to MacBeths castle and is welcomed by Lady MacBeth. The dramatic irony behind this is Lady MacBeth knows that soon Duncan will be coming to his end as king and will suffer the fate of death.
“And his great love, sharp as his spur, hath holp him, to his home before us. Fair and noble hostess, We are your guest tonight.”
That’s exactly right. This comes right after the scene where Lady Macbeth want’s to fill herself with dire cruelty. Nice work.