The Golden Rule
2. Why Overkill is (Usually) a Good Thing
Think of amperage as the "supply" and your device's needs as the "demand." A power supply with a higher amperage rating is like having plenty of supplies on hand. Your device will only take what it needs, and the extra capacity just sits there unused. It's perfectly happy, and so is your device!
So, back to our original question: can you use a 5V 2A charger for a 5V 0.5A device? Generally, yes. The device will only draw 0.5A, and the charger will happily provide it without breaking a sweat. It's like offering someone a whole pizza when they only want a slice — they'll just take the slice and leave the rest.
There are, however, a couple of very rare exceptions to this rule. In some very specific and unusual circumstances, a poorly designed power supply might deliver a "dirty" or unstable voltage when not operating near its maximum capacity. This is extremely rare with modern power supplies from reputable brands. But if you notice your device acting strangely (glitching, restarting, etc.) after switching to a higher amperage charger, it could be a sign of this issue. If that happens, switch back to the original charger and consult the device manufacturer.
In short, don't stress too much about having "too many" amps. As long as the voltage is correct (5V in this case), a higher amperage rating is almost always perfectly safe and, in fact, can even be beneficial. It can mean the charger runs cooler and lasts longer, since it's not being pushed to its limits.
