As the carriers of thoughts, linguistic metaphors serve as the expressive media of cognition in public discourse, and they form an important research perspective in public discourse analysis. Currently, metaphorled public discourse analysis generally bases itself on Conceptual Metaphor Theory (CMT). Such studies analyze the psychological generation of conceptual metaphors in public discourse from the perspective of bodily experience, but they do not tackle the interconnectedness and systematicity of linguistic metaphors in use. Drawing on a Complex Systems Theory (CST) approach to metaphors, this paper studies linguistic metaphors framing the BRICS in English newspapers, focusing on their systematicity in meaningmaking. This paper finds that in public discourse, linguistic metaphors form systematic metaphors, metaphor scenarios and metaphorical narratives in a bottom-up manner, with one leading to another, and such emergence is jointly influenced by discourse purposes, social culture, linguistic contexts, and cognitive activities. This paper concludes that the CST approach can effectively contribute to describing the systematicity of linguistic metaphors in use, and it helps to reveal the rhetorical and argumentative functions of linguistic metaphors in public discourse.