Radak: This refers to darkening of the luminaries. It is a sign of evil for the nations. Therefore, it says "v'Al Malchei ha'Adamah."

Radak citing Ibn Ezra: Tzeva ha'Marom are the angels who stand to help one nation and prosecute another nation, like is explicit in Sefer Daniel. Therefore, it says "v'Al Malchei ha'Adamah", for kingship of the Goyim is stuck to the kingship of the angels.

Malbim: After revealing the secrets of evils that will come on Yisrael, he begins to inform what will be at the end of the days of anger, when the time of the eternal redemption will be. Tzeva ha'Marom are the Sarim (angels) of the Nochrim, or supreme powers from Mazalos and stars that indicate for them existence and success. After, He will [pay] the Nochri kings who will come to help Gog and Magog, like it says in Yechezkel.