the phrase 'must have' can be used as a noun to describe something that one considers essential, desirable or vital to life. It is often used in personal contexts when referring to items of clothing, style, beauty, home décor, cars, technology, and more. When used in this way, the word 'must have' expresses a need to possess or acquire the item in question.
I saw the most stunning dress yesterday – it’s a must have for the upcoming party season!
Her living room is filled with must-haves in modern home décor.
People nowadays say that a good smart phone is a must have.
a helpful tip to keep in mind when using 'must have' as a noun is to be aware of the specificity of the need. Must-haves are concerned with desired items or lifestyle standards, not an essential that is absolutely necessary in order to survive.