Angels are just, good, wise and discerning

2 Samuel 14:17, 20 “And now your servant says, ‘May the word of my lord the king secure my inheritance, for my lord the king is like an angel of God in discerning good and evil. May the LORD your God be with you.’ ” ... "Your servant Joab did this to change the present situation. My lord has wisdom like that of an angel of God--he knows everything that happens in the land."

(Also see 19:27 And he has slandered your servant to my lord the king. My lord the king is like an angel of God; so do whatever you wish.) 

These words spoken by the wise woman of Tekoa in two instances are really asides and we should be careful not to make too much of them. They do appear, however, to recognise a wisdom and discernment in the minds of angels that is beyond what we ordinarily find among men. Justice and goodness are also implied. These creatures are highly intelligent and they have not only a mental dexterity but also a moral integrity that remains untouched by sin. This enables them to know good from evil with great insight.

Angels do not marry or have sexual relations

Matthew 22:30 At the resurrection people will neither marry nor be given in marriage; they will be like the angels in heaven.

When Jesus says that at the resurrection, people will be like the angels, he cannot mean in every respect. He is narrowing down to the fact that they will not marry (or have sexual relations, presumably) which, far from being bad news, means that they will become like the angels who, being spiritual creatures, do not marry (or engage in sexual activity). Angels relate to one another as do brothers and sisters. This would seem to preclude the idea that the Nephilim of Genesis 6 were heavenly creatures rather than earthly.