Can a Eurail Global pass be used within a city such as Paris or will we need a metro pass?
Local, public transportation is not include with most passes. And a waste of money. A global pass in Italy probably will not be cost effective.
You need a separate metro pass or tickets for each city. In-city transport systems that are covered by rail passes (on your counted rail travel days) are rare and primarily found in Germany (S-Bahn only) and Switzerland (with Swiss Travel Passes only).
We get Eurail passes for train travel but you'll need metro or bus passes for cities and their metro systems and buses.
Also, do you know that you have to pay extra to ride the TGV high speed long distance trains in France, and that you have to pay extra for trains higher than Regionale (that's most of them) throughout Italy?
That's if you are using a Eurail pass.
There aren't those extra charges if you use a normal ticket.
Also, do you know that you have to make your French TGV reservations (the ones that incur that extra cost, and you do have to make them because everybody has to have an assigned seat) very early and commit to specific train times because the French ration those TGV pass holder reservations quite severely?