And another angel came out of the temple which is in heaven... This angel will not be a messenger as per the last set. Rather, he will be sent to do a job. The Lord Himself told us about the angels that will harvest his earth at the end time(s).

Mat 13:36-43
36 Then Jesus sent the multitude away, and went into the house: and his disciples came unto him, saying, Declare unto us the parable of the tares of the field.
37 He answered and said unto them, He that soweth the good seed is the Son of man;
38 The field is the world; the good seed are the children of the kingdom; but the tares are the children of the wicked [one];
39 The enemy that sowed them is the devil; the harvest is the end of the world; and the reapers are the angels.
40 As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world.
41 The Son of man shall send forth his angels, and they shall gather out of his kingdom all things that offend, and them which do iniquity;
42 And shall cast them into a furnace of fire: there shall be wailing and gnashing of teeth.
43 Then shall the righteous shine forth as the sun in the kingdom of their Father. Who hath ears to hear, let him hear.

...he also having a sharp sickle. This angel will be given a sharp sickle with which to cut down and harvest the souls of those of those who have followed the beast. When we consider that at this time the Church will have already been taken up and that a remnant of the Hebrew seed is being preserved in the "wilderness," we can conclude that like the angel in the last 1/2 of this set, this angel will use his sickle to cut people off of the "vine of the earth" — i.e., the Gentiles (those without a covenant with God). That there is less said about the activities of the angel in the first half of this set than there is in the last half of this set is probably significant in that the "cutting down and harvesting" will be only partial for this half — a removal of the very offensive, if you will, leaving the "seed" that Christ will use to repopulate His earth for the Millennium.

And another angel came out from the altar...Is is significant that this angel came out from the "altar." The word altar is used in Revelation chapter 6 referring to the souls under the altar that were martyred for Christ Jesus. It is used in Revelation chapter 8 concerning the golden censer filled with the prayers of the saints. But surely God also had in mind the shed blood of Christ, the lamb of God, Who died on the cross for the sin of the world — thus fulfilling all of the blood sacrifices offered on the altars in Old Testament times. And now we see this angel coming out from the altar with a message to deliver..
...which had power over fire... The final destruction of the world will not be with water as with the flood, but with fire (II Peter 3:1-13); the angel with fire is now in place.
The sacrifices of the Old Testament of which Christ Jesus was the antitype were not only of blood but also of fire. It is the "fire element" of the Son of God's sacrificial atonement on the cross that God will have in mind in His final reckoning with man. Just how Christ paid the sin debt in full for man on the cross, only God knows; but we are given to understand that for all who reject His sacrificial atonement, the lake of fire will be their eternal destiny.

...and cried with a loud cry to him that had the sharp sickle... Could this be referring back to the angel of the first half of this set who will be put to work again at the end of the Kingdom Age?

...saying, Thrust in thy sharp sickle, and gather the clusters of the vine of the earth; for her grapes are fully ripe.

As with the times of the flood and of Sodom and Gomorrah, the every imagination of man at this time will undoubtedly be evil continually — man will be "ripe" for the judgment and wrath of God.

19 And the angel thrust in his sickle into the earth, and gathered the vine of the earth, and cast it into the great winepress of the wrath of God.

This seems self-explanatory.

20 And the winepress was trodden without the city, and blood came out of the winepress, even unto the horse bridles, by the space of a thousand and six hundred furlongs.

And the winepress was trodden without the city... (For an interesting study, go to the Bible Study Treasure — the Blue Letter Bible [one of our favorite sites]  and type in the expression "without the city.")
It will help us to understand the expression "without the city" if we go back to Old Testament times and the evangelistic intent of God for the Hebrews. It was always God's intentions and instructions for the seed of Abraham to be a light unto all of their neighbors.

Ex. 12:48-49
48 And when a stranger shall sojourn with thee, and will keep the passover to the LORD, let all his males be circumcised, and then let him come near and keep it; and he shall be as one that is born in the land: for no
uncircumcised person shall eat thereof.
49 One law shall be to him that is homeborn, and unto the stranger that sojourneth among you.

Ezekiel 3:18
When I say unto the wicked, Thou shalt surely die; and thou givest him not warning, nor speakest to warn the wicked from his wicked way, to save his life; the same wicked man shall die in his iniquity; but his blood will I require at thine hand.

However, the Jews turned in on themselves and became "racists" towards the Gentiles around them, considering them to be "dogs" and content to let them remain in their sin.

When Jesus returns to the earth, we are told that He will set up His theocratic government that will rule the world from Jerusalem. Consequently, in the Kingdom Age, Israel should become to the earth an evangelistic nation as it was originally intended to be. If this be so, then under Christ, Israel will be a light to the world. And if this be so, then it would explain why there is no Gentile Church prophesied for the Kingdom Age — for the Gentiles will come to the God of Abraham by coming to the chosen city of Jerusalem where the Lord Jesus will have His throne. Therefore, the winepress of God's wrath being "trodden without the city" speaks to the ungodly that will be left on the earth for this time of God's wrath and judgment: i.e., this language identifies those during the Kingdom Age who will have steadfastly refused to come to Jerusalem and worship King Jesus, the Son of God — their Creator.

...and blood came out of the winepress, even unto the horse bridles... This expression probably means that this will be a bloody, violent time, which can be anticipated since all flesh on the earth — and there will probably be a lot — will be destroyed. (The next four sets of Daniel's 70th Week will go into the details of how the winepress will be screwed down on the inhabitants of the earth during the seven-year period of God's wrath and judgment.)

...by the space of a thousand and six hundred furlongs. [fur·long = a unit of distance equal to 220 yards (about 201 meters)]
This number--a thousand and six hundred-- seems to have a spiritual / prophetic meaning; so, let's apply Scriptural Numerology.

6 = the number of man
x 100 = the number of full productivity
= 600 or the full productivity of fallen man

100 = the number of full productivity
x 10 = the number for full responsibility
= 1,000 in this case, the number indicates full responsibility for full productivity

Therefore, in Scriptural Numerology, the number one thousand and six hundred indicates the full productivity of fallen man — who is incapable of doing any good of himself (our righteousness is as filthy rags) — as well as the full responsibility for that productivity. If anyone doubts that man has responsibility for what he produces in this life, we need but to read the words of Jesus. But keep in mind as you read this that Jesus took the full responsibility for our sin debt upon Himself on the cross so that "whosoever" will believe can receive Him as Lord and Savior and be delivered from all the curses that sin has brought upon the human race.

John 15:19-23
19 If ye were of the world, the world would love his own: but because ye are not of the world, but I have chosen you out of the world, therefore the world hateth you.
20 Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you; if they have kept my saying, they will keep yours also.
21 But all these things will they do unto you for my name's sake, because they know not him that sent me.
22 If I had not come and spoken unto them, they had not had sin: but now they have no cloke for their sin.
23 He that hateth me hateth my Father also.

John 3:17-21
17For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.