A bucket with a hole drilled through its lid works perfectly as a primary fermenter in brewing. You may choose to add a spigot to the side, which will allow you to tap the liquid off without fussing with siphons or having to lift a pail full of heavy liquid.
There is a commercially available version called the “Ale Pail” (which is technically a 6.5 gallon bucket) which comes pre-manufactured with a spigot, air vent and measurements up the side.
I’ve also seen mash tuns made with 5 gallon buckets, and have been told that they will hold heat well, but I am suspicious. I prefer to use 10 gallon coolers to do my mashing in, since they are already insulated against heat loss (although they are more expensive)
If you have come here interested in home brewing, but are a beginner to the craft, I highly recommend listening to the Basic Brewing podcast.