so we book in advance metro or train rides and we show up late can the ticket be used for the next schedules rides?
you don't book metro rides -- you show up and take the next train
for others it depends. TGV and Thalys involve specific seats on specific trains; miss it and you have lost the ticket
for TER and similar slower trains it depends on the ticket you have. The tickets from machine that you validate before boarding can be used on any train; if you book on line, it is for a specific train. Also with trains booked ahead, some tickets are unchangeable (very early very cheap tickets) and some are changeable. I managed to book one let of several trips this summer the wrong way -- luckily I noticed and was able to change it before the trip; if I had not, then because I had a specific seat and time, it would have been gone and I would have had to buy a new ticket.