Spot metering is just a camera feature that measures the exposure from a single point. However, it is often misunderstood, and utilizing spot metering correctly may widen your technical capabilities when shooting in manual mode. Whether you are shooting in automatic or manual mode, cameras always measure the reflected light and tries to give you the correct exposure. Different metering modes have their own area of use; therefore, it is hard to say that one mode is better than the other. However, you should choose your exposure metering mode carefully, as cameras tend to give underexposed or overexposed readings in certain scenarios.
Spot metering measures the light from a very small portion, usually less than 5% of the total image area. This provides an advantage in scenes where the subject is either brighter or darker than its surrounding. Even this mode seems quite straight forward, it still requires practice and correct use of exposure compensation for achieving accurate results.
In this 15 minute video, nature photographer Steve Perry explains spot metering in detail and demonstrates how he achieves accurate exposures each time. He also explains when to use and when not to use spot metering, by sharing examples from wildlife photography scenarios.