In Exodus 3:2 & Genesis 18,19 use the word “angel”, I heard that the word
could mean “messenger”. If it is so, is it possible that Jesus could be
this “messenger”?

You are not the first one to propose that the “angel” in
Exodus 3:2 could in fact be Jesus, the Son of God. Below is the text in
its context:
Meanwhile Moses was tending the flock of his father-in-law Jethro, the
priest of Midian. Leading the flock across the desert, he came to Horeb,
the mountain of God. 2 2 There an angel of the LORD appeared to him in
fire flaming out of a bush. As he looked on, he was surprised to see that
the bush, though on fire, was not consumed. 3 So Moses decided, “I must
go over to look at this remarkable sight, and see why the bush is not
burned.” 4 When the LORD saw him coming over to look at it more closely,
God called out to him from the bush, “Moses! Moses!” He answered, “Here I
am.” 5 God said, “Come no nearer! Remove the sandals from your feet, for
the place where you stand is holy ground. 6 3 I am the God of your
father,” he continued, “the God of Abraham, the God of Isaac, the God of
Jacob.” Moses hid his face, for he was afraid to look at God. 7 But the
LORD said, “I have witnessed the affliction of my people in Egypt and have
heard their cry of complaint against their slave drivers, so I know well
what they are suffering. 8 4 Therefore I have come down to rescue them
from the hands of the Egyptians and lead them out of that land into a good
and spacious land, a land flowing with milk and honey, the country of the
Canaanites, Hittites, Amorites, Perizzites, Hivites and Jebusites. 9 So
indeed the cry of the Israelites has reached me, and I have truly noted
that the Egyptians are oppressing them. 10 Come, now! I will send you to
Pharaoh to lead my people, the Israelites, out of Egypt.” 11 5 But Moses
said to God, “Who am I that I should go to Pharaoh and lead the Israelites
out of Egypt?”

This passage seems to clearly have “the God of your father
Abraham” speaking from the bush. This seems to mitigate against the idea
that it was the Son of God speaking from the bush. A more interesting
question is why it even says that an angel spoke at all, given that when
Moses spoke to the flame in the bush, it was God, YHWH, who spoke back.
Could the word angel (messenger) be a reference to God, or could a
separate messenger have spoken first. I would say that the answer is that
we cannot be sure. However, the idea that this was Jesus seems unlikely,
at least to me. I certainly would not be dogmatic about this one.

By the way, there are a number of places in the Old Testament
where theologians and others have speculated that a very powerful
spiritual being found there are in fact Jesus Christ. Examples would
include the one Joshua met on the road to Jericho:
While Joshua was near Jericho, he raised his eyes and saw one who stood
facing him, drawn sword in hand. Joshua went up to him and asked, “Are you
one of us or of our enemies?” 14 He replied, “Neither. I am the captain
of the host of the LORD and I have just arrived.” Then Joshua fell
prostrate to the ground in worship, and said to him, “What has my lord to
say to his servant?”

It is my opinion, that this is more likely to be an Old
Testament vision of the Son of God.

John Oakes