Is it legal to put a videos on YouTube to blogger

is it legal to embed Youtube Videos on your blogs IF you are NOT using the videos to sell anything?

Or, even if you are selling stuff, but not using the video "directly" for selling your products or affiliate products, is it ok to have a video on your blog that may be helpful to your customers because it is related to your product?:confused:

Or, what if you just think it's a cool video and you wanna embed it?