Three Metals in the Mishkan and the Avos

You probably know that in this week’s parsha Bnei Yisroel donated three types of metal for the construction of the Mishkan. But did you know that the Midrash teaches that these three metals in the Mishkan’s structure represent our three Avos - Avraham, Yitzchok and Yaakov?! [See Midrash Shemos Rabba 49:2]