I have to admit; as a solo female traveler new to Europe I was very nervous about using Paris metro. I read lots of horror stories online about pick pocketing on the Metro/RER, & almost cancelled my trip because of it. In retrospect I’m so glad I didn’t.
I figured out the metro system pretty quick; it’s a very fast, inexpensive, & efficient way to see Paris. I ended up buying a Navago card; 10/10 recommend. It was good for a week; super cheap (I think it was $28). Pass allowed me unlimited use of metro and RER with Paris proper. The pass requires photo ID to be affixed to the card within 48 hours of purchase. I had color photo copies of all my documents, including my US drivers license, so I cut my photo ID, and it fit perfectly on the card.
I also brought a tiny metro map which I discretely referred to a few times in the beginning to make sure I was going the right way. There are also large maps all over the metro stations as well.
From a safety standpoint I saw only one attempted pickpocket. I educated myself quite a bit on how to identify them, what tactics they use, and how to protect myself.
Pickpocketing is a crime of opportunity. I recommend leaving most cash/passports/cards in hotel safe. I brought my ID, one credit card, my phone, and no more than $100 with me each day.
Avoid backpacks, and carrying luggage on Metro; that screams tourist. Also keep bling at home. Do not take your phone out on Metro while getting on or off in order to avoid it being snatched out of your hand. I used a cross body purse that was slash resistant, with a zipper that locked made by PacSafe. This purse was amazing, & pickpocket proof. It has all these separate compartments to keep your essentials safe, and also protects your credit cards from being hacked remotely.
Overall I felt safe on metro; no one messed with me because I blended in with locals, and I knew exactly where my belongings were at all times. The only time I was a little nervous was when I took the wrong train and ended up towards St. Denis (north east), which is a sketchy part of town.