Different metals are important and sought for different reasons.
gold
A metal sought after during the Klondike was gold.
Gold
Gold was highly sought after during the Klondike.
zinc
Gold, I think.
Metal-bearing rocks sought after in mining are typically called ore deposits. These deposits contain high enough concentrations of valuable metals such as copper, gold, silver, or iron to be economically viable for extraction. Mining companies prospect for ore deposits to extract and process the valuable metals.
In my opinion, copper is pretty sought after
The word sought is likely "crutches" (wooden or metal walking supports).
it sought to contain the spread of communism
importance metal
The base metal is iron.