Some trust in chariots and some in horses, but we trust in the name of the Lord our God. (Ps 20:7)
Gerald H. Wilson writes in his commentary on Psalms:
Like Psalm 18 before it and Psalm 21 immediately after, Psalm 20 is one of the “royal psalms” and is explicitly concerned with the military activities of the Israelite king. In this psalm the army speak to the king in a long series of jussive forms (20:1-4, 5b), expressing their desire for divine assistance and ultimate victory. … at the time of an impending military campaign, it was not unusual for the king, people, and army to seek divine assistance through prayer, fasting, and temple liturgy. Our psalm represents one such liturgical entreaty of divine assistance. In its original setting, the psalm would have functioned as a sort of pledge of loyalty by the army to their ruler before embarking on a military campaign. …
Structurally, the liturgy in this psalm falls into four parts: 1) Hopes for divine intervention and victory (v.1-5); 2) assurance of divine support (v. 6); 3) confession of trust in Yahweh (v. 7-8); and 4) a final plea directed to Yahweh (v. 9). (The NIV Application Commentary Vol. 1. Zondervan ©2002 p. 381-382)
This Psalm, which has been referred to as “Israel’s National Anthem,” is a national song of war. It also points to the believer’s spiritual warfare, as he calls upon his coming king, Jesus Christ in the day of battle. Just as the army in this Psalm prepares for battle through spiritual means including, shouts of joy (v. 5), setting up banners (v. 5) and trusting the LORD (v. 7), so we are told in the New Testament that the weapons of our warfare are not of the flesh (2Cor 10:4), and we do not wrestle against flesh and blood (Eph 6:12). Read Ephesians 6:10-20 to remind yourself of what weapons you are equipped with in your battle.
One of the greatest tools in our defensive arsenal is TRUST. We could think of trust as the handle on our shield of faith. Time and again in the Old Testament, God had Israel outnumbered and overwhelmed, so that it would be through their trust in Him that they would emerge victorious. Likewise in our battle against Satan, sin, and this world, we can only stand firm and not fear as we place our trust solely and solidly upon the LORD our God. While those in this world rely upon physical means, typified by the horses and chariots of verse 7, the believer must never trust in earthly things for his deliverance. It’s not that God does not protect through earthly means, He does, but ultimately our trust is not in that thing which we see with our eyes, but in He who is our defense.