The Transit Access Pass, or TAP card, was designed to eventually replace bus, subway and train passes across all public transit systems in Los Angeles County.
To promote the use of the new system, Metro will provide complimentary TAP cards to customers who do not already have one when they buy a $5 day pass until April 11, or until supplies run out, according to Metro.
After that, the plastic cards will cost $2 each.
The rechargeable cards, which have been used in other cities for decades, will be sold at vending machines.
Coins and bills will still be accepted on MTA buses and trains, even after the TAP conversion comes, Metro officials said.
The TAP card is part of a $89 million project to upgrade obsolete fare boxes on buses and to turnstiles and improved fare collection gear on Metro's subway and light rail lines.
The TAP card will also be adopted by smaller transit agencies, such as Santa Monica's Big Blue Bus, with the goal of one day spreading the system countywide so that a single card can be used to pay for fares everywhere.