This option is preferable since wall gutters that are used on seam roofs are the task of professionals who cover the roof of the house.
How to install gutters on a metal roof.
For self assembly the easiest way is to use a suspended type of structure which provides for fastening the gutter to special hooks located along the eaves.
If you are using metal materials you may need to slide the gutter into the gutter brackets from the opposite end.
Crimp three times across both long edges and twice on the narrow sides.
Either way the gutter brackets should clip around the top of the half round gutter length to hold it securely in place.
A gutter cover or gutter heating system might be just what you need for your metal roof.