Michal was the youngest daughter of King Saul, and the first wife of King David. When David refused her older sister Merab, Michal let it be known that she loved the young warrior who had of late been outperforming her father in battle. Merab was given to Adriel the Meholathite, instead, to whom she bore five sons.
When David asked about the dowry for Michal, Saul deviously asked for one hundred foreskins from Philistine victims. Fearlessly, David defied the odds and killed two hundred enemy soldiers, bringing the foreskins as proof of his sincerity. After David had taken his bride, Saul attempted to get through to David by way of his daughter. He sent assasins to kill him at his residence, but she helped her husband escape, lying when asked, leaving the impression that David had threatened her.
When Saul became envious of David to the point of sending men to kill him, Michal helped David run away while she set up an image in his bed, making it look like he was ill and sleeping. When Saul's messengers found the image, Saul asked why his daughter deceived him, and Michal said that David threatened to kill her unless she let him go.
As the feud with the king continued, David acquired more wives, such as Abigail, wife of Nabal. During that campaign, Saul worked behind the scenes, annulling the marriage of David and Michal and giving her to Palti the son of Laish, who was from Gallim. After Saul had died, and David was fighting Saul's son Ishbosheth for control of the kingdom, David demanded that Michal be returned to him. Against the pleas of her second husband, Michal returned to the house of David, now king of Israel.
However, she no longer loved David. She showed her disdain for him when he led a processional when the ark of the covenant was brought into Jerusalem. She disapproved of such unbecoming behavior—dancing in the lowly garb of a servant—and let him know it. As a result, she was banned from his harem, never to have any children by him again.
However, as a move perhaps to bring embarrassment to David, Michal apparently adopted her sister Merab's sons, raising them for her husband Adriel. In doing this, she was potentially providing a future king from her father's house (since she had none of her own). When the time came, years later, she would betray her nephews, turning them over to be executed by the Gibeonites as payment for her father's crimes.