Is there a concealer that effectively covers spots, freckles, and blemishes?

I’ve tried using products that are advertised as good, but they still haven't been able to cover the spots, melasma, and blemishes on my face. I have so many spots that look like freckles, and the melasma and blemishes are beyond description. I want to find my holy grail concealer; are there any you would recommend?