It would have 'melted your heart' [=it would have filled you with compassion, sympathy, etc.] to see her lying in that hospital bed.
Her anger 'melted away' when she saw that he was truly sorry.
He seemed to 'melt into' thin air. [=he seemed to disappear]
(..) between the two absolutely identical belts"... and you should have seen the look she gave me! I thought the flesh was gonna melt off her face. It's not funny. She's not happy unless everyone around her is panicked, nauseous or suicidal. And the Clackers just worship her. - The who? (..)2006 The Devil Wears Prada