What can we know about these beings?
Were they male and/or female?
What did they look like?
How have they acted?
What do they do?
Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee. 
But to which of the angels said he at any time, Sit on my right hand, until I make thine enemies thy footstool? Are they not all ministering spirits, sent forth to minister for them who shall be heirs of salvation? 
Whereas angels, which are greater in power and might, bring not railing accusation against them before the Lord. 
angel (ân´jel), bodiless, immortal spirit, limited in knowledge and power, accepted in the traditional belief of Judaism, Christianity, and Islam. The three choirs of angels appear early in the Christian era; the classes are, from the highest: seraphim, cherubim, thrones; dominations, virtues, powers; principalities, archangels, angels. Angels appear in the Bible, often in critical roles, e.g., visiting Abraham and Lot (Gen. 18; 19) and announcing the Incarnation to Mary (Luke 1). The cult of guardian angels who protect individuals or nations is especially strong in the West. The angels of HELL, or devils, led by SATAN, are viewed as initiators of evil temptations.
The Concise Columbia Encyclopedia is licensed from Columbia University Press. Copyright © 1991 by Columbia University Press. All rights reserved.
angel (ân´jel) noun
1. a. Theology. An immortal, spiritual being attendant upon God. In medieval angelology, there are nine orders of spiritual beings. From the highest to the lowest in rank, they are: seraphim, cherubim, thrones, dominations or diminions, virtues, powers, principalities, archangels, and angels. 
b. The conventional representation of such a being in the image of a human figure with a halo and wings.
2. A guardian spirit or guiding influence.
3. a. A kind and lovable person. b. One who manifests goodness, purity, and selflessness.
4. Christian Science. God's thoughts passing to man.
5. Informal. A financial backer of an enterprise, especially a dramatic production or a political campaign.
[Middle English, from Old English engel and or Old French angele, both from Late Latin angelus, from Late Greek angelos, from Greek, messenger.]
- angel´ic (àn-jèl´îk) or angel´ical adjective
- angel´ically adverb
The American Heritage Dictionary of the English Language, Third Edition is licensed from Houghton Mifflin Company. Copyright © 1992 by Houghton Mifflin Company. All rights reserved.
Selected Illustrations from the Concise Columbia Encyclopedia.  Copyright © 1991 by Columbia University Press.
And the angel of the LORD appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed.
4397 malÕak { mal-awk'} 
from an unused root meaning to despatch as a deputy; TWOT - 1068a; n m
AV - angel 111, messenger 98, ambassadors 4, variant 1; 214
GK - 4855 { Ja;l]m'
1) messenger, representative
1a) messenger
1b) angel
1c) the theophanic angel
The Ben Elohim saw the daughters of Adam, that they were fit extensions. And they took wives for themselves from all those that they chose...The Nephilim  (Those who fell, or ... the fallen ones) were in the earth in those days, and even afterwards when the Ben Elohim CAME IN TO the daughters of Adam, and they bore to them--they were Powerful Ones which existed from ancient times, the men of name.
(from the Interlinear Hebrew Bible Genesis 6)
And the angels (Ben Elohim, Sons of God) which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
Note that the word "wives" here does not necessarily mean they, the Ben Elohim, were wed to these women. They merely took those they wanted. Much as we hear about today as women are taken up by UFO's and subjected to various scrutinizing.
For hundreds of years the Nephilim corrupted the earth and oppressed mankind. The Bible states that the giants existed before this earth age, before the flood and even after that time, Genesis 6:4.
Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves (the angels) over to fornication, and going after strange flesh,5are set forth for an example, suffering the vengeance of eternal fire.  
Why did the angels go after strange flesh? They were supposed to be  ministers of the creation of God not the usurpers. This contradicts tradition but is historically upheld by accounts in Exodus where descendants of the Nephilim are encountered in Cannan by the Israelites. The Apocryphal Book of Enoch, a 1st century BC extra Biblical manuscript quoted by Jude and John, detailed events of the fallen angels. It describes their punishment and even their names. Some of the Nephilim perished, at least their bodies perished, beneath the waters of the flood. The leaders of this rebellious act were chained until judgment day at various locations in the earth. 
Were these "Sons of God" the same as the angels of Heaven?
What have we to do with thee, Jesus, thou Son of God?
Fact: Jesus was the and a Son of God.
Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
Fact:We shall be like him when he appears.
For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
Fact:The Sons of God are as angels, but not necessarily created angels.
For the earnest expectation of the creature waiteth For the manifestation of the sons of God. 
We are going to see in this study facts concerning who the sons of God, who are like angels, really are.
5207 huios { hwee-os'} 
apparently a primary word; TDNT - 8:334,1206; n m
AV - son(s) 85, Son of Man + 444 87 TDNT 8:400, 1210, Son of God + 2316 49, child(ren) 49, Son 42, his Son + 848 21, Son of David + 1138 15 TDNT 8:478, 1210, my beloved Son + 27 
+ 3350 7, thy Son + 4575 5, only begotten Son + 3339 3, his (David's) son + 846 3, firstborn son + 4316 2, misc 14; 382
GK - 5626 { uiJov" }
1) a son
1a) rarely used for the young of animals
1b) generally used of the offspring of men
1c) in a restricted sense, the male offspring (one born by a father and of a mother)
1d) in a wider sense, a descendant, one of the posterity of any one,
1d1) the children of Israel
1d2) sons of Abraham
1e) used to describe one who depends on another or is his follower
1e1) a pupil
2) son of man
2a) term describing man, carrying the connotation of weakness and mortality
2b) son of man, symbolically denotes the fifth kingdom in Daniel 7:13 and by this term its humanity is indicated in contrast with the barbarity and ferocity of the four preceding kingdoms (the Babylonian, the Median and the Persian, the Macedonian, and the Roman) typified by the four beasts. In the book of Enoch (2nd Century) it is used of Christ.
2c) used by Christ himself, doubtless in order that he might intimate his Messiahship and also that he might designate himself as the head of the human race, the man, the one who both furnished the pattern of the perfect man and acted on behalf of all mankind. Christ seems to have preferred this to the other Messianic titles, because by its lowliness it was least suited to foster the expectation of an earthly Messiah in royal splendour.
3) son of God
3a) used to describe Adam (Lk. 3:38)
3b) used to describe those who are born again (Lk. 20:36) and of angels and of Jesus Christ
3c) of those whom God esteems as sons, whom he loves, protects and benefits above others
3c1) in the OT used of the Jews
3c2) in the NT of Christians
3c3) those whose character God, as a loving father, shapes by chastisements (Heb. 12:5-8)
3d) those who revere God as their father, the pious worshippers of God, those who in character and life resemble God, those who are governed by the Spirit of God, repose the same calm and joyful trust in God which children do in their parents (Rom. 8:14, Gal. 3:26 ), and hereafter in the blessedness and glory of the life eternal will openly wear this dignity of the sons of God. Term used preeminently of Jesus Christ, as enjoying the supreme love of God, united to him in affectionate intimacy, privy to his saving councils, obedient to the Father's will in all his acts
For synonyms see entries 3808, paidarion; 3813, paidion; 3814, paidiske; 3816, pais; and 5043, teknon.
See entry 5868 for comparison of synonyms.
444 anthropos { anth'-ro-pos} 
from 435 and ops (the countenance, from 3700), man-faced, i.e. a human being; TDNT - 1:364,59; n m
AV - man 552, not tr 4, misc 3; 559
GK - 476 { a[nqrwpo" }
1) a human being, whether male or female
1a) generically, to include all human individuals
1b) to distinguish man from beings of a different race or order
1b1) of animals and plants
1b2) of from God and  Christ
1b3) of the angels
1c) with the added notion of weakness, by which man is led into a mistake or prompted to sin
1d) with the adjunct notion of contempt or disdainful pity
1e) with reference to two fold nature of man, body and soul
1f) with reference to the two fold nature of man, the corrupt and the truly Christian man, conformed to the nature of God
1g) with reference to sex, a male
2) indefinitely, someone, a man, one
3) in the plural, people
4) joined with other words, merchantman6
435 aner { an'-ayr} 
a primary word cf 444; TDNT - 1:360,59; n m
AV - man 156, husband 50, sir 6, fellow 1, not tr 2; 215
GK - 467 { ajnhvr }
1) with reference to sex
1a) of a male
1b) of a husband
1c) of a betrothed or future husband
2) with reference to age, and to distinguish an adult man from a boy
3) any male
4) used generically of a group of both men and women
We see first that the word son or sons here relates to a "son" or offspring. Next, we see the reference is to a human type versus animal, male or female. Now, after the fact that it is a human we see that there is a sexual type namely male.
So, if we have established the fact they are male, where are the females if there are no female angels?
For this cause ought the woman to have power (authority in sign or under the power of her husband) on her head because of the angels.
And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof; And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man.  And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.
Notice that woman was taken out of man after the creation of man. There was no woman prior to the creation of Adam. The lineage of Adam is given in the new testament, therefore prior to roughly 6000 yrs ago there was no flesh and no woman, therefore no female angel. If man and wife are "one flesh", there is no need for there to be female angels in heaven. Woman was taken out of man and therefore shall she return to man.
Nevertheless neither is the man without the woman, neither the woman without the man, in the Lord. 
  Bone of my bones and flesh of my flesh, they are one.
120 Õadam { aw-dawm'} 
from 119; TWOT - 25a; n m
AV - man 408, men 121, Adam 13, person(s) 8, common sort + 7230 1, hypocrite 1; 552
GK - 132 { µd;a;
 } & 133 { µd;a;
 } & 135 { µd;a;
1) man, mankind
1a) man, human being
1b) man, mankind (much more frequently intended sense in OT)
1c) Adam, first man
1d) city in Jordan valley9
The primitive root for 'woman' in the lexicon is Õanash indicating the fallen state of man and his inability to redeem himself.
605 Õanash { aw-nash'} 
a primitive root; TWOT - 135; v
AV - incurable 5, desperate 1, desperately wicked 1, woeful 1, sick; 9
GK - 631 { vWna;
 }* & 653 { vn"a;
1) to be weak, sick, frail
1a) (Qal)
1a1) to be incurable
1a2) to be sick
1a3) desperate, incurable, desperately wicked, woeful, very sick (pass participle) (metaph.)
1b) (Niphal) to be sick10