Whom does the verse address?
Radak: It addresses Yerushalayim.
What is the significance that light came?
Radak #1: Light is a metaphor for Simchah and good; Targum Yonasan is 'the time for your redemption has come.' darkness is the opposite, i.e. affliction and evil that will come. Ori is a command.
Radak #2: Your light set. This is like "u'Va ha'Shemesh" (Vayikra 22:7). Your light in this world set. In place of it, you will have great light - salvation and Simchah; "Lo Yihyeh Lecha Oh ha'Shemesh l'Or Yomam" (below, 19). This is all a metaphor.
Malbim: Leave the darkness (affliction), and illuminate to the entire world. Your physical and spiritual salvation came.
How did Hashem's honor shine on you?
Malbim: It is the supreme honor, from the influence of Divine light on His Nevi'im and remnants.
