A spirit being is invisible just like wind or air is to the unaided eye. The wind and the air are real, just as spirit beings are real, and they have substance just as wind does. But the unaided eye is not able to spot them, so the ability to see something that is spirit, or composed of spirit, is not in us by nature. Though it is not there naturally, the ability to perceive them can be given.
This is what Elisha means: "Give him the ability to see what is around us." And so the young man apparently saw a tremendous army of spirit beings who were ready to do battle in Elisha's behalf should anything occur. They were there all the while, invisible but nonetheless there.
John W. Ritenbaugh
Image and Likeness of God (Part Four)
It is likely that Elisha could not literally see all of these spirit beings that were out there on the mountain. But by faith, through the eyes of faith—because he knew God, because he was close to God—he understood that God was with Him always and a tremendous army of angelic beings protected His servant Elisha.
Whether that army was always there is a moot point. They may have been there simply because the Syrian army was there. It does not matter whether there was one or many angels. It is really an indication of God through Elisha and through the vision to this young man that wherever God is things are weighted in our favor. We have no need to fear the many who may come against us.
We need to realize that there are more for us than there are against us, and a great deal of spiritual activity is taking place around us that we are not physically able to discern. Nevertheless, it is there. God is showing us here that this is true. God intends this section to give us some encouragement.
From this, we ought to be able to understand that God is greater than any emergency we might find ourselves in. He tells us in Psalm 34:7, "The angel of the LORD encamps all around those who fear Him and delivers them." This man of God understood by spiritual discernment that things were going on around him, and by the same token, because we have the Spirit of God, we should also be sensitive to this because God's Word shows that this is indeed occurring.
Most people only see what is human. In fact, physically, that is all we can see. But we have to know—it has to be part of the way, the means, or the wherewithal by which we act. Jesus Christ, a divine Spirit, is the guiding force of His church. He tells us He will never leave us or forsake us. Just as sure as there are spirit beings who rule and guide the church, there are spirit beings who rule and guide the world. We see both sides of it here.
John W. Ritenbaugh
Satan (Part 3)