Base metals are ones which are key and proxy to the economic activity.
They comprise of aluminium, copper, nickel, zinc, lead, etc.
They are a part of our day to day life too like copper in utensils, nickel in batteries, zinc in supplements, etc.
As these are mainly industrial metals, they drive most of their demand from activities which are cyclical in nature. Hence an investment in them at a right time can give a decent return.
An exposure can be made in these through ETFs and stocks dealing in them.
In India, companies like Hindustan copper, Hindustan Zinc, etc. are in the mining of these metals and are a play and proxy to the metal cycle.