What do we learn from "Hashem ba'Shamayim Hechin Kis'o"?
Radak: He is like a king who sits above everything. If Shamayim is His throne, everything - Shamayim and Eretz are below Him, and in His Reshus.
Radak citing Shocher Tov: There are four haughty ones in the world - the lion is haughty over all Chayos, the ox over all Behemos, the Nesher over all birds, and man rules over all of them - "u'Rdu bi'Dgas ha'Yam uv'Of ha'Shamayim?" (Bereishis 1:28). Hashem put the four haughty ones on [the legs] of His throne, to show that He is haughty over all of them. The Targum of "Ki Ga'o Ga'ah" (Shemos 15:1) is 'He is haughty over all haughty ones.'
Malbim: His Kisei, i.e. conduct, is in Shamayim. It is based on natural laws fixed in Shamayim. Even so, His kingship rules over all - He conducts also via Hashgachah and rules over the Ma'arachah to conduct according to deeds, reward and punishment, to pay Tzadikim like their actions.
What is the meaning of "Mashalah"?
Rashi: [His kingship] rules. (Past tense used in place of present.) Radak - this repeats the beginning of the verse.
Malbim: Refer to 103:19:1:3.
