my metro zte has a light that blinks constantly even off the charger but it wont turn on? how do i turn it on the battery can

If it keeps blinking, on or off the charger, you probably need the battery replaced.

I believe that phone has a the 'hard to remove' type of battery, so if that is the case, and if the phone is still under warranty, then you should contact the manufacturer about it and not try to do it yourself which would void the warranty.

If the phone isn't under warranty anymore, or it is an easy remove battery, then you can do it yourself. Just make sure you don't get a cheap after market battery. It never turns out well.