A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 46:1Upon Alamoth--most probably denotes the treble, or part sung by female voices, the word meaning "virgins"; and which was sung with some appropriately keyed instrument (compare Ch1 15:19-21; see on Psa 6:1, title). The theme may be stated in LUTHER'S well-known words, "A mighty fortress is our God." The great deliverance (Kg2 19:35; Isa 37:36) may have occasioned its composition. (Psa 46:1-11)
refuge--literally, "a place of trust" (Psa 2:12).
strength-- (Psa 18:2).
present help--literally, "a help He has been found exceedingly."
trouble--as in Psa 18:7.
psa 46:2The most violent civil commotions are illustrated by the greatest physical commotions.
psa 46:3swelling--well represents the pride and haughtiness of insolent foes.
psa 46:4God's favor is denoted by a river (compare Psa 36:8; Zac 14:8; Rev 22:1).
city of God, the holy place--His earthly residence, Jerusalem and the temple (compare Psa 2:6; Psa 3:4; Psa 20:2; Psa 48:2, &c.). God's favor, like a river whose waters are conducted in channels, is distributed to all parts of His Church.
most High--denoting His supremacy (Psa 17:2).
psa 46:5right early--literally, "at the turn of morning," or change from night to day, a critical time (Psa 30:5; compare Isa 37:36).
psa 46:6(Compare Psa 46:2).
earth melted--all powers dissolved by His mere word (Psa 75:3; Hos 2:22).
psa 46:7with us--on our side; His presence is terror to our enemies, safety to us.
refuge--high place (Psa 9:9; compare also Psa 24:6, Psa 24:10).
psa 46:8what desolations--literally, "who hath put desolations," destroying our enemies.
psa 46:9The usual weapons of war (Psa 7:12), as well as those using them, are brought to an end.
psa 46:10Be still, &c.--literally, "Leave off to oppose Me and vex My people. I am over all for their safety." (Compare Isa 2:11; Eph 1:22).