Angels are condemned with Satan if they are evil

Matthew 25:41 Then he will say to those on his left, 'Depart from me, you who are cursed, into the eternal fire prepared for the devil and his angels.' 

The cursed, fallen, evil angels will one day be condemned with their leader Satan and be cast into the eternal fire prepared for them.

Angels revealed and announced the resurrection of Christ

Matthew 28:2-7 There was a violent earthquake, for an angel of the Lord came down from heaven and, going to the tomb, rolled back the stone and sat on it. His appearance was like lightning, and his clothes were white as snow. The guards were so afraid of him that they shook and became like dead men. The angel said to the women, "Do not be afraid, for I know that you are looking for Jesus, who was crucified. He is not here; he has risen, just as he said. Come and see the place where he lay. Then go quickly and tell his disciples: 'He has risen from the dead and is going ahead of you into Galilee. There you will see him.' Now I have told you."

Luke 24:2-7 They found the stone rolled away from the tomb, but when they entered, they did not find the body of the Lord Jesus. While they were wondering about this, suddenly two men in clothes that gleamed like lightning stood beside them. In their fright the women bowed down with their faces to the ground, but the men said to them, "Why do you look for the living among the dead? He is not here; he has risen! Remember how he told you, while he was still with you in Galilee: 'The Son of Man must be delivered over to the hands of sinners, be crucified and on the third day be raised again.'"

Angels strengthened Jesus as he came to the cross

Luke 22:43 An angel from heaven appeared to him and strengthened him.

Matthew 26:53 Do you think I cannot call on my Father, and he will at once put at my disposal more than twelve legions of angels?

Only Luke mentions this. As the angel appeared only to Jesus it may be wondered how Luke knew. It is suggested that such a change came over the Saviour that it was obvious to the disciples who then passed it on, Luke discovering ti when he wrote his Gospel.

Matthew Henry says of how when Christ was in his agony and there appeared to him an angel from heaven, strengthening him that this was a part of his humiliation - that he was thus strengthened by a ministering spirit.

Angels tell people not to be afraid when they appear

Genesis 21:17 God heard the boy crying, and the angel of God called to Hagar from heaven and said to her, "What is the matter, Hagar? Do not be afraid; God has heard the boy crying as he lies there.
Luke 1:13 But the angel said to him: "Do not be afraid, Zechariah; your prayer has been heard. Your wife Elizabeth will bear you a son, and you are to call him John.

Luke 1:30 But the angel said to her, "Do not be afraid, Mary; you have found favor with God. 

Luke 2:10 But the angel said to them, "Do not be afraid. I bring you good news that will cause great joy for all the people. 

Matthew 28:5 The angel said to the women, "Do not be afraid, for I know that you are looking for Jesus, who was crucified. 

Angels often startle people and make them afraid when they appear

Daniel 10:4-8  On the twenty-fourth day of the first month, as I was standing on the bank of the great river, the Tigris, I looked up and there before me was a man dressed in linen, with a belt of fine gold from Uphaz around his waist. His body was like topaz, his face like lightning, his eyes like flaming torches, his arms and legs like the gleam of burnished bronze, and his voice like the sound of a multitude. I, Daniel, was the only one who saw the vision; those who were with me did not see it, but such terror overwhelmed them that they fled and hid themselves. So I was left alone, gazing at this great vision; I had no strength left, my face turned deathly pale and I was helpless.
Luke 1:12 When Zechariah saw him, he was startled and was gripped with fear. 

Luke 2:9 An angel of the Lord appeared to them (the shepherds), and the glory of the Lord shone around them, and they were terrified.

Matthew 29:2-4 There was a violent earthquake, for an angel of the Lord came down from heaven and, going to the tomb, rolled back the stone and sat on it. His appearance was like lightning, and his clothes were white as snow. The guards were so afraid of him that they shook and became like dead men.

Gill notes how in the case of Zechariah he was troubled, and fear fell upon him; for such appearances of angels were not now so common as formerly: and when they were more usual, generally had such effects on the minds, even of good men and in the case of the shepherds - at the sight of such a personage, and at such unusual light and glory about them: they ... not used to such appearances ... were awed with the majesty of God, of which these were symbols, and were conscious to themselves of their own sinfulness and frailty.

Angels always obey God

Psalm 103:20, 21 Praise the LORD, you his angels, you mighty ones who do his bidding, who obey his word. Praise the LORD, all his heavenly hosts, you his servants who do his will.

Instinctively and immediately angels always obey God's commands. This is the main basis for the part of the Lord's prayer wherewe are to ask that God's will be done on earth as in heaven.

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. 

Angels came and attended Jesus tempted in the wilderness

Matthew 4:11 Then the devil left him, and angels came and attended him.

Gill says that these angels came to Jesus in a visible, human form, as they were used to do under the Old Testament dispensation, which seems likely. It happened after the temptation was over; after Satan was foiled, and was gone. The timing shows that Christ alone had got the victory over him, without any help or assistance from the angels. Gill understands them as bringing him food of their own, as with Elijah, (1 Kings 19:5,-8) to satisfy his hunger and refresh him

Thus, says Gill, as the angels are ministering spirits to the heirs of salvation, both in a temporal and in a spiritual sense, (Hebrews 1:14 ) so they were to Christ. Nothing is more frequent with the Jews than to call the angels "ministering angels".

Spurgeon says that the enemy left him when he had shot his last bolt ... for a season .... So soon as the evil one had departed, angels appeared to fulfil a ministry for which they eagerly longed, but which the presence of the devil hindered. No doubt they had been hovering near, waiting their opportunity. These holy beings might not come upon the scene while the battle was being fought, lest they should seem to divide the honours of the day; but when the duel was ended, they hastened to bring food for the body and comfort for the mind of the champion King. It was a battle royal, and the victory deserved to be celebrated by the courtiers of the heavenly King. Let us behold, these angels, learn from their example, and believe that they are also near to all the warriors of the cross in their hour of conflict with the fiend. O Tempted but Triumphant King, thy servants worship thee, and ask permission and grace to minister to thee as angels did!

Mark 1:13 is parallel
and he was in the wilderness forty days, being tempted by Satan. He was with the wild animals, and angels attended him. 

Angels will accompany Christ when he returns

Matthew 16:27 For the Son of Man is going to come in his Father’s glory with his angels, and then he will reward each person according to what they have done.

Mark 8:38 If anyone is ashamed of me and my words in this adulterous and sinful generation, the Son of Man will be ashamed of them when he comes in his Father’s glory with the holy angels.

Luke 9:26 Whoever is ashamed of me and my words, the Son of Man will be ashamed of them when he comes in his glory and in the glory of the Father and of the holy angels.

Matthew Poole says that Luke repeats the first two most perfectly, as here recorded. Mark expounds Luke’s words, where he saith that Christ shall come in his own glory, and in his Father’s and of the holy angels. By the glory of the holy angels is meant no more than attended by the holy angels, according to Matthew 13:41 and 1 Thessalonians 4:16 and other scriptures.

1 Thessalonians 4:16 says

For the Lord himself will come down

with a loud command,

with the voice of the archangel and

with the trumpet call of God,

and the dead in Christ will rise first.

There appears to be some parallelism here - the loud command is the voice of an archangel and can be pictured as the trumpet call of God. Christ calls the dead from their graves. He does so by sending his holy angels, led by the archangel, to gather the elect.

At the same time (Matthew 13:41) the angels will weed out all evil

The Son of Man will send out his angels, and they will weed out of his kingdom everything that causes sin and all who do evil.

Angels will be weeders out and harvesters at the end

Matthew 13:39, 41, 49 ... and the enemy who sows them is the devil. The harvest is the end of the age, and the harvesters are angels. ...

The Son of Man will send out his angels, and they will weed out of his kingdom everything that causes sin and all who do evil. ...

This is how it will be at the end of the age. The angels will come and separate the wicked from the righteous

We learn in this parable that the angels will be the harvesters of people at the end of the age. Sent by Christ they will weed out everything that causes sin and all who do evil. .. They will separate the righteous from the wicked at the end.

Spurgeon says on these verses

Now is the time of growing: the harvest hastens on, and the reapers are already chosen by the great householder. We may rejoice that angels, and not men, are the reapers. At what hour the consummation of the age (RV) shall come we do not know, but it is surely drawing nigh. ... This the Son of man will do with authority; the angels are simply the executioners of the wrath of the Lamb. ... The separation between “the wicked” and “the just”, who are in the kingdom, will be at the close of the dispensation. It will be accomplished by the messengers of God, the appointed angels: it will be done infallibly, readily, fully, and finally. The doom of the wicked is described in terms which are terrible to the last degree. ....

Matthew Henry says

The reapers are the angels: they shall be employed, in the great day, in executing Christ’s righteous sentences, both of approbation and condemnation, as ministers of his justice, ch. 25:31. The angels are skillful, strong, and swift, obedient servants to Christ, holy enemies to the wicked, and faithful friends to all the saints, and therefore fit to be thus employed. He that reapeth receiveth wages, and the angels will not be unpaid for their attendance; for he that soweth, and he that reapeth, shall rejoice together (Jn. 4:36 ); that is joy in heaven in the presence of the angels of God.

The angels of heaven shall come forth to do that which the angels of the churches could never do; they shall sever the wicked from among the just; and we need not ask how they will distinguish them when they have both their commission and their instructions from him that knows all men, and particularly knows them that are his, and them that are not, and we may be sure there shall be no mistake or blunder either way.