You permitted it when you bought a carrier branded phone and signed the purchase contract. In return for the deep discount (or free) you get for the phone, you agree that the carrier can install software. Usually it's games, but it looks like Metro decided Its users want news on their lock screens.
------------------------------------------------------------- Please mark any response that helped you as your solution. -------------------------------------------------------------
Or you can go to the Metro Play app, click on the 3 lines in the upper right-hand corner (settings), then go down to "Disable Lockscreen" on the menu, check one of the answers, then click "Disable" and they're gone.
