Metsad is a mountain stronghold or natural fortress — a fortified high place, often a rocky peak used as a defensive position. It appears in historical narratives about David's wilderness years, when he hid in the strongholds (metsadot) of the wilderness from Saul. The city of Masada takes its name from this word.
David's time in the metsad (stronghold) was a school of trust. Unable to rely on palace or army, stripped of status, he ran to rocky fortresses and called God his ultimate stronghold. Psalm 18:2 identifies God as 'my rock, my fortress (metsudah), my deliverer.' The physical stronghold becomes a living metaphor: just as the rocky mountain is impregnable to enemy attack, so God's protection is insurmountable. This theology of refuge runs from David through to the Book of Revelation, where God is the ultimate fortress of His people.