Will Sagos survive in a metal pot between zone 8 &7? Being metal, does it get too hot in summer and cold in winter for roots?
No this will not survive in these areas. Even if it could, the type of metal that you use can have negative effects on the plant. For example: copper will kill roots, as will aluminum. Steel would be good as long as there is drainage.
Either way, it will not stand the cold temperatures of that area. Unless you can bring it in, then it will die in the cold.
I recommend keeping it in a HDPE or LDPE plastic, as most plant containers are. Also, keep the container small enough to be able to carry. You will need to bring it in and out often.
Here is an article for more information on the care of sago palms: https://www.gardeningknowhow.com/ornamental/trees/sago-palm/how-to-care-for-sago-palms.htm