The phrase "be the missing link" is a correct and usable phrase in written English.
You can use it when you want to describe something that ties two previously unrelated things together. For example, "This new technology could be the missing link that finally brings us the energy solutions we have been searching for."
With a smart feature set and the right price, the Fit could be the missing link from fitness device to smartwatch the market has so far been missing.
Customer obsession could be the missing link.
It's a salty-rich-sweet combination that seems to be the missing link in my diet.
"Is my father going to be the missing link who is going to make sense of it all?
It has even been suggested that ontologies could be the "missing link" between legal theory and Artificial Intelligence.
The Jets jettisoned Pennington in August after trading for Favre with the idea that, hallelujah, he would be the missing link.
A representative and (at least partly) elected local patient congress could be the missing link in democratic transition to the assembly.
Data can be the "missing link" for a company that has never had access to the side of your customers that only you can see.
And who knows, since it works so well for Davies, that her signature, personal evidence-based technique will not turn out to be the missing link in the light-touch paradise adumbrated in early coalition documents.
"Some researchers now think sleep may be the missing link when it comes to overall health, safety, and productivity," says Darrel Drobnich, the senior director of government and transportation affairs for the National Sleep Foundation.
In 2005, two biologists called David Raubenheimer and Stephen Simpson put forward the "protein leverage hypothesis", in which they argued that protein could be the missing link in the obesity crisis.
