The first metal card pictured is from the 1984 Topps Gallery of Immortals/Champions Bronze set of 12. The 1984 set was actually the first set of 12 metal cards ever released in either Bronze or Silver parallel editions (no aluminum until 1986). No sets were released in 1983.
Aside from the Aluminum, Bronze, and Silver 12-card Base sets from 1984-1991, and the one card a year Bronze Premiums for a total of 9-cards from 1983-1991. There was also one more GC set released (not pictured).
The Gallery of Champions Pewter Bonuses was an 8-card set released one every year from 1984-1991 similar to the Bronze Premium set. The difference between the Pewter Bonuses and the Bronze Premiums (beside material) is that the Pewter Bonuses were parallel cards to the base set and the Bronze Premiums were not.
What I have shown here are 6 different metal cards from the 1988 GC Aluminum set.
The 1988 Aluminum set was probably the most massed-produced set of the entire series, and represents a good starting point for someone looking to get into metal cards.
Before 1988, the GC Aluminum sets were not sold with their own display cases ('86-'87). The 1988 GC Aluminum set is the first Aluminum set to come with its own case; a practice that continued through 1991.
Being the most affordable set, I purchased 4 extra '88GC Aluminum sets just for the extra display cases that I used to hold the '83-'91 Bronze Premiums, '84-'91 Pewter Bonuses, '86 Aluminums, and '87 Aluminums.
I haven't quite completed the entire series of Gallery of Champions yet because I'm still missing the Pewter Bonuses from 1984 and 1990. I don't collect the Silver sets due to price. I'm still on the fence with the Bronze Base sets from 1986-1991 since I was able to complete those in the Aluminum version. I had no choice but to get the Bronze versions for 1984-1985.
I thought that I'd just summarize up the Gallery of Champions series for anyone that may be interested in them, but still on the fence about collecting them. It can be a little confusing for "complete-ists" since some of the releases are parallels, while others are considered premiums or bonuses.
Existing price guides are completely out of sync with the market value for these metal cards, so I'll post something on my "Grading and Pricing" page that I've developed based on my experience buying and selling these. It'll remain a work in progress.