In order for Terraform to run operations on your behalf, you just need to create an API Keys from your personal profile.
Create your personal Access Token.
curl -X POST \
-H "Content-Type: application/json" \
-H "X-Auth-Token: <API_TOKEN>" \
"https://api.equinix.com/metal/v1/user/api-keys" \
-d '{
"description": "string",
"read_only": false
}'
curl -X GET -H 'X-Auth-Token: <API_TOKEN>' \
"https://api.equinix.com/metal/v1/user/{id}/api-keys"
export METAL_AUTH_TOKEN=