Big, meaty king crab legs are a luxurious treat that's great simply served with melted butter for dipping. They're sold precooked and frozen, or defrosted by the market prior to sale. Be sure to buy from a fishmonger you trust, because lower-quality crab may taste of ammonia or freezer burn, EricMM says on Chowhound.
Because king crab legs are already cooked, you can simply defrost them if frozen, then crack them open and enjoy the meat cold. You may want to give them a rinse to remove excess salt, jbsiegel says. Once thawed, they can contain lot of water, so kseiverd snips the shells open with kitchen shears and sets the legs on end in a paper-towel-lined container to drain before serving.
If you'd rather have the crab hot, there are several methods you can use to warm it. Chowhound dave_c steams the legs for about five minutes on the stove, while Njchicaa says that it's easy to steam larger quantities by wrapping them in foil and throwing the packets on the grill. You can also heat them briefly directly on the grill grates. Slitting the shells first imparts a welcome bit of smokiness if you've got a charcoal grill, FishTales says. And for an indoor alternative to steaming, MGZ puts the legs on a rack in a large roasting pan and heats them in the oven at 225 degrees Fahrenheit.