Ohms Law, Ohms Law, Ohms Law.
If the voltage is 9V and the load is 30 ohms (for example), the current taken by the load is:-
I = \$\dfrac{V}{R}\$ = 9/30 = 300mA.
If your power supply (or battery pack) is capable of supplying 1000 amps it still has to obey ohms law and that means I = V/R and if the load is 30 ohms it'll take 300mA from a 9V power source.
Don't connect your meter (measuring current) across your battery because you'll measure the full output current from the battery and this might damage your meter or burn small wires.
You current charger is rated at 500mA and is adequate - this means your load takes 500mA or less (maybe 300mA as per my math above). You don't need to measure this to know this.
HOW CAN I MEASURE THE MAX CURRENT OF THE BATTERIES OR SOME
POWER SUPPLY???
Put your meter back in its case and make sure the leads are plugged back into measuring voltage because you might forget next time you use it across the AC in your home and then there will be smoke and it'll be your meter burning possibly.
If you want to know how much current a battery can produce, look at its data sheet and don't try measuring it.