There are many types of milk depending on the pasteurization methods or the fat content. There is also processed milk. Try to use different kinds of milk according to the types of tea. Basically clean tasting milk is best for Thé au Lait using delicate green tea. For green tea, oolong tea orjasmine tea, low-fat milk or vegetal cream is recommended.
As for full-bodied black tea, rich tasting milk is suitable. When making Chai style tea with houjicha, deeply roasted oolong tea or matcha, add a little evaporated milk to regular milk. With the characteristic matcha aroma the taste will become more profound. In any case, start with a small amount of milk and then add more after tasting.