Who or what is the angel of the Lord in the Bible?

TL;DR:

The angel of the Lord in the Bible is the preincarnate Christ. Christ’s presence is still with His people, guiding, providing, and empowering us to live for Him.

There has been much debate regarding the identity of the angel of the Lord in the Bible. At times, Scripture refers to the "angels of the Lord" or "an angel of the Lord." However, on other occasions "the angel of Lord" speaks as God Himself. These appearances are a Christophany (pre-incarnate appearance of Christ) or a theophany (appearance of God in human form). When the angel of the Lord appears, He speaks as God, identifies Himself as God, and has the same responsibilities as God. Passages in which this is the case include Genesis 16:7–12; 21:17–18; 22:11–18; Exodus 3:2; Judges 2:1–4; 5:23; 6:11–24; 13:3–22; 2 Samuel 24:16; and Zechariah 1:12 and 12:8. In some of these appearances, those present claimed they had seen the Lord. Interestingly, the term "the angel of the Lord" no longer occurs after the birth of Jesus in human form since Jesus came to earth. He is still with us and guides, provides, and empowers us to live for Him today.

from the old testament

In Genesis 16:7–14, the angel of the Lord appeared to Hagar in the wilderness, promising her that her descendants will be numerous and reassuring her about her son's future.
The angel of the Lord also intervened during Abraham's near-sacrifice of Isaac, stopping him and providing a ram for the offering instead. He also reiterated the promise of blessing for Abraham’s obedience (Genesis 22:11–18).
In Exodus 3:2, the angel of the Lord appeared to Moses in the burning bush, calling him to lead the Israelites out of Egypt and revealing God's name.
The angel of the Lord is mentioned as guiding and protecting the Israelites on their journey to the Promised Land and carrying out God's plans against their enemies (Exodus 23:20–23).
The angel of the Lord appeared to Gideon, commissioning him to deliver Israel from the Midianites and performing a sign to confirm his message (Judges 6:11–24).
In Judges 13:3–21, the angel of the Lord appeared to Manoah and his wife, announcing the birth of Samson and providing instructions about his Nazarite vow.
In 2 Samuel 24:16, the angel of the Lord halted the plague ravaging Israel.
The angel of the Lord appeared to Zechariah in a vision, interceding for Jerusalem and providing messages about the future of the city (Zechariah 1:11–17).

from the new testament

The angel of the Lord is not mentioned in the New Testament because Jesus came and took on flesh (John 1:14).

implications for today

The angel of the Lord’s appearances throughout the Bible reveal to us God’s divine intervention, guidance, and protection still available for us today. We recognize that just as the angel of the Lord played a pivotal role in guiding and reassuring the people we read about in the Bible, so, too, does God continue to offer guidance and support in our lives today. He pursues us and guides us (Proverbs 3:5–6), calling us to find life in Him (John 10:10). As we recognize His sovereignty, we are reminded of our deep dependence on Him, and as we come to know His heart and desires for us, we long for His presence, wisdom, and sustaining power. Our understanding and solutions are limited compared to His infinite wisdom. God’s care and provision are unlike anything else. Reading about the angel of the Lord reminds us to trust in God’s plans even when faced with uncertainty, to remain steadfast in faith, seek God’s direction in all aspects of life, and to recognize that He is actively involved in our lives, providing for our needs and directing our paths.

understand

The angel of the Lord speaks and acts with divine authority in the Old Testament.
The term "the angel of the Lord" is not used after Jesus' birth, indicating a shift to Christ's incarnate presence.
The appearances of the angel of the Lord highlight God's active involvement, providing guidance, protection, and reassurance to His people.

reflect

How does understanding the angel of the Lord as a preincarnate Christ impact your view of God's presence and intervention in your life today?
How can you recognize and respond to God's guidance and protection in your daily experiences, reflecting on the ways the angel of the Lord guided and protected biblical figures?
How does the transition from the angel of the Lord to the incarnate Christ influence your relationship with God and your understanding of divine intervention?

engage

Interestingly, the term "the angel of the Lord" no longer occurs after the birth of Jesus in human form. However, the appearance of the angel in Matthew 1 to Joseph may show a flaw in this claim. In Matthew 1:24 we read, "When Joseph woke from sleep, he did as the angel of the Lord commanded him." This was after he was told by "an angel of the Lord" in a dream, "Joseph, son of David, do not fear to take Mary as your wife, for that which is conceived in her is from the Holy Spirit" (Matthew 1:20). So it seems that "the angel" is a reference back to "an angel." This is a good reminder that context matters for rightly interpreting the Bible—the angel of the Lord is not necessarily a reference to a pre-incarnate Christ in every single occurrence.
There is another view regarding "the angel of the Lord,” referring to an angel speaking on God's behalf. In the ancient world, the messenger of a king held equal status with the king himself. His word was equal to the king's word. One could rightly say, "The king said," even if only the messenger had spoken the words. This also alleviates the problem with people "seeing God" since the Bible elsewhere says, "No one has ever seen God" (John 1:18; 1 John 4:12). The primary problem with this view is that those who said they had "seen the Lord" were either mistaken or viewed seeing God's messenger (the angel) as equal with seeing God.
In what ways can the examples of the angel of the Lord’s interactions with people in the Bible inspire and challenge us to seek God's guidance and intervention in our lives personally and communally?