The federal government has certain express powers (also called enumerated powers) which are powers spelled out in the Constitution, including the right to levy taxes, declare war, and regulate interstate and foreign commerce. In addition, the Necessary and Proper Clause gives the federal government the implied power to pass any law "necessary and proper" for the execution of its express powers.
What are the expressed powers? 
the right to levy taxes, declare war, and regulate interstate and foreign commerce.