Thermite is a pyrotechnic composition of metal powder fuel and metal oxide. When ignited by heat, thermite undergoes an exothermic reduction-oxidation (redox) reaction.Most varieties are not explosive but can create brief bursts of high temperature in a small area.opper(II) thermite reactions can be so fast that copper thermite can be considered a type of flash powder. An explosion can occur and send a spray of copper drops to considerable distance. Copper(I) thermite has industrial uses in e.g. welding of thick copper conductors ( cadwelding ).