Explain why igneous rocks do not contain fossils.

Fossils can not be formed in igneous rock because before it cooled from the liquid magma state, any renants of fossils would be destroyed and melted ... they form in sedimentary because thats where they can be buried and perserved the easiest, metamorphic would destroy them from the pressures and temperatures involved in there formations

Any fossils that would have been in the original rocks would have melted when magma formed.