Shield Motor L293D Low voltage on the way out

Using Arduino Motors, Mechanics, Power and CNC
1

Im feeding the motor with a 9V battery,but on the way out the voltage is only 0.5V, and the motors don't works well, what is the problem?

2

what is the problem?

The problem is:-

Im feeding the motor with a 9V battery

Those 9V batteries do not have the current capacity to drive a motor.

3

By an order of magnitude, they are good to perhaps 50mA continuous, small motors
are around 0.5 to 2A