Milkshakes are thick, delicious ice cream drinks, and while malts may look very similar, there is one key (yet simple) difference between the two: the addition of malt powder.
Malt powder is made from malted grain, typically malted barley combined with wheat extract. Malted milk powder has a rich nuttiness to it—imagine a Cheerio, but slightly sweeter.
The earthiness works particularly well to show off some other classic profiles like chocolate and vanilla. The malt powder rounds out the flavor and gives it a fuller body.
Malts take the basic milkshake and, with a scoop of malted milk powder, makes it into something more magical. They are thicker, more filling, and have a toastier flavor to them.