There's a part of David's face that's always shaded, always pointed away from the reader.
He rejects Saul's firstborn daughter by appealing to his modest roots, "Who am I, and what is my family or my father's clan that I should become the king's son-in-law?" (18:18).
David is feigning modesty.
He later takes Michal, Saul's younger girl when Saul offers her to whomever pays him in "100 Philistine foreskins." David has bloodlust. He seizes the challenge for Michal's hand, kills a hundred Philistines and circumcises their dead corpses for her hand in marriage.
Michal is little more than a trophy that he soon disposes of. He bags other women he stumbles into (Abigail, Bathsheba, Ahinoam). Surely, this was a thorn in Michal's side. A thorn that, despite her attempts to suppress it, would pinch and twist through her husband's military campaigns and the songs that the women sang of him.
Some time later, after Saul had died, David danced and "exposed himself" (allegedly to praise the Lord for not killing an ark-bearer), the thorn twisted in her side, and when she got a moment alone with him, Michal quipped sarcastically, "How the king of Israel honored himself today!" Yeah, you might think David's reply, that he was "dancing before the Lord", was God-honoring. But what did he say after that? "I was dancing before the Lord who chose me over your father..." He is speaking to a girl whose father died in combat and who chose David as her husband (who, for all David knew, did so not vindictively). There's just something diabolically gleeful about his reply here.
When Achish offered him solace from Saul's hunting men, David says, in a style of groveling that is becoming all too familiar, "If I have found favor with you, let me be given a place in one of the outlying towns, so I can live there. Why should your servant live in the royal city with you?" Achish is a Philistine. For all his life David was fighting the Philistines. In fact, he is carrying the very same sword that he used to behead Goliath the Philistine. And here, he grovels at Achish's feet and calls himself his servant. His duplicity is not arbitrary. To the contrary, it's expedient. He picks an outlying town to inhabit. A place less likely to be raided by Saul's men than Achish's loft.
There's just something dark about him. Something not told in the official story about David.
