As I've discussed on the blog before, choosing the correct fats in your diet is critical for overall health. But within the healthier fats category, there are even more nuances to consider, including which fats to use for hot and cold uses.
To start off, fats that are saturated in molecule structure tend to hold up to high heat cooking fairly well, as they contain no double bonds. These fats include lard, butter, ghee, bacon fat, duck fat, tallow (beef fat), palm oil, and coconut oil. You'll want to use these fats for sauteing and roasting vegetables or any other high heat cooking method.
Fats that are better for cold uses include olive oil, sesame oil, nut oils (walnut, pecan, macadamia), avocado oil, and limited amounts of flaxseed oil. These oils are monounsaturated or polyunsaturated, meaning they contain one or more double bonds, making their molecular structure a bit more unstable (hence why they don't hold up to heat as well). These fats are great for homemade salad dressing, mayo, and other condiments.
Other fats that should be avoided for hot and cold uses include vegetable oils (canola, corn, soy, grapeseed, sunflower, safflower, rice bran), margarine, hydrogenated or partially hydrogenated oils, and fake butter spreads. These fats are man-made or highly processed and are easily oxidized or rancidified by light, air, or heat. Oxidized fats are never healthy to consume, as they are toxic and highly inflammatory to the body.
So, in all practicality, I would recommend having the following fats on hand for hot uses - butter and coconut oil - and the following for cold uses - avocado and olive oils. You'll be all set for whatever recipe you come across, and your body will thank you too.