Angels holy and unholy

There are at least three references to holy angels in the New Testament.

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. 

Revelation 14:10  ... they, too, will drink the wine of God's fury, which has been poured full strength into the cup of his wrath. They will be tormented with burning sulfur in the presence of the holy angels and of the Lamb.

By implication fallen, non-elect angels are not holy. The holy angels, Gill notes, will be judges and will condemn unbelievers to everlasting burnings and pronounce the sentence on them. They will gather them out and seperate them from the righteous, cast them into the furnace of fire, will be spectators of their punishment and rejoice at it. The sight of their power and glory will increase the torment of the sufferers.

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.