The term 'metallic percussion sound' can be described as a whang, which is a five-letter word. A whang is a sharp, ringing sound that is produced when metal objects are struck together. It is often used in musical instruments such as cymbals and gongs, as well as in everyday objects like door knockers. The sound of a whang is distinct and recognizable, and it is often used to create a sense of urgency or excitement.