paragraph: As we will see, most metrics for similarity between vectors are based on the dot product. The dot product acts as a similarity metric because it will tend to be high just when the two vectors have large values in the same dimensions. Alternatively, vectors that have zeros in different dimensions-orthogonal vectors-will have a dot product of 0, representing their strong dissimilarity.
answer: The dot product acts as a similarity metric because it will tend to be high just when the two vectors have large values in the same dimensions.