There are 2 parts of this opinion:

The chartering of the Bank was w/in the constitutional power of federal gov’t because it bore a reasonable relationship to constitutionally-enumerated powers of gov’t (power to collect tax, borrow money, regulate commerce)

Since Bank was Constitutionally chartered, the tax was unconstitutional.  Marbury saw possibility that this taxation by state could be carried to extremes and lots of things could be taxed.  M disposed of the argument of the states that the Bank was not Constitutionally chartered because the powers come directly from the states.  M says powers come from the PEOPLE.  M says that all powers need not be EXPLICIT.  They can be implied. “necessary and proper” (most significant part of the opinion) – M rejected opinion that necessary meant “absolutely necessary”.  Says all means which are appropriate are OK.  Therefore, all means are rationally related to a constitutionally specified object the means is constituational.  M says power to punish for violation of federal laws is implied; post offices; roads, implied.
Marshall also believes that the S. Ct. should strike down laws only when it is quite clear that no constitutionally-specified object was being pursued.  Anything closer should be left to Congress – not courts!
Marbury’s argument like taxation w/o representation.  You can’t tax people who don’t have a say in the affairs of the state.  M says taxes on federal government violate the supremacy clause.
McCulloch today-The court shows great deference to congress and will not inquire into legislators’ motives.  Therefore, as long as legislation is rationally related to one constitutionally-enumerated motive that Congress might have been pursuing . . . the fact that other ends not w/in the enumerated powers might have been achieved does not invalidate that power.