An enemy, a mugger, a tsunami, a fire, a race, and even glitter that gets everywhere: just a few of the metaphors used to describe different aspects of the Covid-19 pandemic since it began in early 2020. Whether consciously or not, people often use metaphor to talk and think about complex, abstract and sensitive subjects. Time, illness and the climate crisis are prime examples of concepts that may be explained through clearcut, accessible imagery. Allusions to journeys, fights and sport help us make sense of things that would otherwise be inexpressible or unknowable. In my research, I have shown how metaphors are central to our understanding of the experience of cancer, chronic pain and mental illness. So when a new invisible virus arrived that was responsible for illness, death and unprecedented disruption, it made sense that metaphor was used to turn something incomprehensible into more familiar, accessible and predictable terms. Throughout the pandemic metaphors have performed a dual role, both explaining the situation and steering behavioural change. Research shows the metaphors we are exposed to affect how we think and feel about problems and their solutions. On 17 March 2020, Boris Johnson described coronavirus as “an enemy” that “can be deadly” but was “also beatable”, and hinted at the resources and sacrifices that would be needed to “win the fight”. For all the criticisms that have been rightly levelled against them, war metaphors have long been known to be effective at persuading people that a problem is serious and urgent enough to require collective effort and a change in behaviour: if we are at war with a dangerous enemy, we need to pull together and be prepared to play our part in defeating it. Fire metaphors have proven to be one of the most powerful ways of conveying the importance of social distancing and the need for continued effort and vigilance. In October 2020, the Welsh government imposed a two-week “firebreak” lockdown (in contrast with the “circuit-breaker” lockdown that failed to materialise in England). In February this year, the director general of the World Health Organization tweeted about a global decline in Covid-19 cases but cautioned: “The fire is not out, but we have reduced its size. If we stop fighting it on any front, it will come roaring back.” Fires evoke vivid images, strong emotions and powerful narratives, and are particularly appropriate for any phenomenon we perceive as “spreading”. When vaccines finally came along, Johnson described them as providing a “wall” of immunity, which can function as defence both against metaphorical enemies and against metaphorical waves. One columnist explained the speed of vaccine development had resulted from the fact that processes which usually happen sequentially had taken place “as if a restaurant brought out your starter, mains, and pudding simultaneously. The cooking time for each is no shorter, but the meal isn’t half speeded up.” And on Twitter, Dr Tom Frieden used Snapchat messages as a metaphor to address the fear that mRNA vaccines can change people’s DNA. Yet the pandemic has also revealed the dark side of metaphors: they can misfire and cause confusion, distraction and obfuscation. War metaphors may have been appropriate at the start of the pandemic, but research has shown that by foregrounding the need for action rather than inaction, they can discourage self-limiting behaviours. This is a major flaw when previously unimaginable self-restraint has been demanded from so many for so long. War metaphors can also be used to legitimise excessive clampdowns on the part of governments, and to justify expectations of heroic sacrifice on the part of professional groups such as teachers. They can also create expectations about a clearcut moment of victory which, when frustrated, can lead to fatalism. It is not a surprise that, after some references to the “bugle of the scientific cavalry” in anticipation of the vaccine rollout, Johnson has shed the military rhetoric (as well as the light-heartedness of “squash the sombrero” and doing “whack-a-mole” on local outbreaks) in favour of sombre warnings of learning to live with the virus. Even “freedom day”, which could suggest the defeat of an enemy keeping us captive, has now mostly been replaced by the much less triumphant “terminus point” for the lifting of restrictions. As early as July 2020, the WHO was critical of the ubiquitous metaphor of multiple “waves” of the pandemic because it underplayed the role of human behaviour in controlling the spread of the virus. As the WHO’s Margaret Harris put it: “We are in the first wave. It’s going to be one big wave.” That did not, however, stop Johnson from saying in March 2021: “On the continent right now you can see, sadly, there is a third wave under way. And people in this country should be under no illusions that previous experience has taught us that when a wave hits our friends, I’m afraid it washes up on our shores as well.” In doing so, he exploited the uncontrollability of literal waves to blame what was happening in other countries for a resurgence of the pandemic in the UK. Even the appeal and accessibility of metaphorical “tiers” and traffic light systems can be undermined by a lack of clarity and consistency in how they are applied. Last autumn, the original tiers 1, 2 and 3 of local restrictions were quickly translated into green, amber and red. However, as tier 1 was officially described as “medium alert”, there was in fact no level of restrictions that properly corresponded to a green traffic light. More recently, the relative clarity of “green”, “amber” and “red” lists for international travel has been undermined by a lack of explicit criteria for changing the status of individual countries from one category to another. Confusion surrounds the introduction of a “green watchlist” of countries that may be imminently downgraded to amber. Metaphors are inescapable. Used sensitively and appropriately, they can help individuals and societies overcome overwhelming, long-term problems such as a global pandemic. But used insensitively or inappropriately, or when undermined by inconsistent actions and policies, metaphors can add to confusion and disillusionment, making problems harder to overcome. In short, to employ another metaphor, they can be a double-edged sword. Elena Semino is professor of linguistics and verbal art at Lancaster University, and director of the ESRC Centre for Corpus Approaches to Social Science. She is author of Metaphor in Discourse and lead author of Metaphor, Cancer and the End of Life