Butter can be a healthy fat if the butter is homemade butter and not store bought butter.
Store bought butters are made of a lot of non natural ingredients and also contains a lot of saturated fat which can raise your cholesterol levels and lead to clogged arteries as well as heart disease, heart attacks strokes etc.
Store bought butter is healthy in moderation but when you eat too much butter it becomes bad for you.
However in moderation the butter has been shown to help keep your heart healthy.
But too much butter can lead to heart issues.
Healthier or healthy fats are things such as olive oil, avocado, nuts, seeds, and fatty fish.
As long as you're eating more healthy foods and other healthy fats your health should be just fine and butter is okay as long as you don't over eat too much of it.