Managing metadata

Simply put, metadata is data about data. In Power Query M, metadata can be associated with any value using the meta keyword to define a metadata record. Metadata in and of itself does not do anything, nor does it change the behavior of a value in any way.

Consider the following query:

let
    x = 10 meta [Type = "Whole number", OoM = 1],
    y = 20 meta [Type = "Whole number", OoM = 1],
    z = 30 meta [Type = "Whole number", OoM = 1]
in
    x * y * z

This query still returns 6000, just as before. However, the metadata associated with each value can be accessed and returned by using the Value.Metadata function, as follows:

let
    x = 10 meta [Type = "Whole Number", OoM = 1],
    y = 20 meta [Type = "Whole Number", OoM = 1],
    z = 30 meta [Type = "Whole Number", OoM = 1]
in
    Value.Metadata(x)[Type]

This query returns Whole Number.

Two additional metadata functions exist, Value...