What would happen if the meter leads were connected to the positive and negative terminals of the battery while the meter and leads were set to read amperes?

If the meter leads are connected to the positive and negative terminals of a battery while set to read amperes, it would create a short circuit condition. The ammeter, designed to measure current, would allow a large current to flow through it, potentially damaging the meter or blowing its internal fuse. Additionally, it could cause overheating or even a fire hazard, depending on the battery's output and the meter's specifications. Proper usage of the meter requires it to be connected in series with a load, not directly across the battery terminals.