GO to HOME compatibility will exist very soon. Here are the steps that can be followed:
Send a Pokemon from Pokemon Go to Pokemon Home.
Open a mystery box in Pokemon Go, allowing you to catch a Meltan.
After doing this, you'll receive a Mystery Gift in Pokemon Home. Open this to get a Gigantamax Melmetal you can transfer to Sword/Shield!
Note that it isn't available just yet, but it seems to be very soon.
Hope I helped!