(Psychological / emotional perspective)
Most metals have symbolic meanings.
They can also be connected with various planets: sun is represented by gold, the moon by silver, mercury by quicksilver, venus by copper, mars by iron, jupiter by tin, saturn by lead.
In dreams these ancient symbolisms begin to surface as we learn more.
For instance, mars the warrior wielding an iron sword suggests that we need to fight our own corner and become more assertive.