What is the significance of the rock crushing the image?
Rashi: The fifth kingship will eradicate and crush all [the previous ones].
Malbim: The rock hints to Even Yisrael, which Hashem will raise. It will not be via man's power.
What is the meaning of "Mah Di Lehevei Acharei Denah"?
Rashi: What will be after this (your kingship).
What is the significance of the order iron, copper, Cheres, silver and gold`?
Malbim: This hints that in the war of Gog and Magog, all Bnei Edom will gather to fight against Yishmael, and they will kill each other, like it says in Yechezkel and Zecharyah. Edom is iron; they will be strong at the time. Copper hints to Yavan ? they will be one kingdom. Silver hints to Paras u'Madai, and gold to Bavel - all of them will be under Yishmael. The iron and copper (Edom and Yavan) will crush Cheres, silver and gold (Yishmael, including Paras u'Madai and Bavel).
