not one's cup of tea

Example: “Horror movies are just not my cup of tea.”

Origin: The positive form came first, which is easy to miss given how the phrase is used now. In British English of the early twentieth century, calling someone your cup of tea was warm praise — it meant they suited you exactly — and the metaphor made obvious sense in a culture where how a person took their tea was a known and particular quirk, a small matter of individual preference everyone was expected to have. The negative construction spread later, from around the 1920s and 1930s, and eventually crowded the affirmative out almost entirely. It survives because it is useful in a way plainer refusals are not: saying something is not your cup of tea declines it as a matter of personal taste while carefully declining to call it bad.