It has bought the shares for £100,000 and it will also receive one warrant for 0.025p with a life of 30 months.
It now owns 6.97% of Thor's capital.
Thor has a portfolio of properties in the Northern Territory, Australia and in Western Australia. Thor also owns the Pilot Mountain tungsten project in Nevada, USA.
Metal's chief executive Paul Johnson said: "Metal Tiger continues to build a diverse range of natural resource investments around what we believe is the bottoming phase in natural resource microcap and junior equities.
"Today's investment is another step in our building process and comes at a time when Thor Mining has recently experienced a strengthening of its finances through the sale of Spring Hill thus enabling it to orientate toward existing and potentially new project development.
"We look forward to monitoring developments at Thor Mining with interest."
Metal Tiger shares eased 2.38% to 4.10p on the day.