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.

Angels shouted for joy when God created the world

Job 38:6, 7 On what were its footings set, or who laid its cornerstone - while the morning stars sang together and all the angels shouted for joy?

God questions Job as to where he was when God created the world. This leads to the reference to the angels adn creation. We know that the angels and all heavenly creatures were created before the creation of this world. Here we learn that the angels shouted for joy when God created the world. The morning stars must be another way to refer to the angels. Jesus is the bright and morning star (Revealtion 22:16) and they are morning stars. Stars speak of glory, purity and light and of constancy, permanency and the numbers points to the fact there are so many angels.

It is rare to find a reference to angels singing in Scripture but that is the implication here. Perhaps the cause of their rejoicing was the anticipation of the work of salvation for which this earth forms the theatre. It may have been simply to do with the creation itself.