What is the significance of the darkness?
Radak: It is a metaphor for afflictions.
Malbim: Choshech is the absence of light 1 .
Why does it say that Hashem's honor will appear on you?
Radak: The matter is repeated in different words; "Hashem" refers to Kevod Hashem. Arafel is vapors and smoke that fill the air also when the sun shines. The Nimshal is, darkness will cover the land. The nations that have no creed, the verse depicts that darkness covers them, to the point that they cannot see light at all. Le'umim refers to Am Yishmael - they have creed, and they believe in [His] unity, reward and punishment... The verse depicts that the sun shines on their horizon, but the Arafel fills the air (Sheker in their Emunah, e.g. denial of choice).
