True standing seam requires tools that a DIY person will not have.

Consider a snap seam instead. Similar look and far easier to install.

Here is one source that I use for all my metal roofing needs, and I've installed this type of roof. Most metal roofing suppliers have a similar product.

https://www.metalsales.us.com/products/vertical-seam/

You will need to find a real lumber yard, or contractors supply -- even my local Ace Hardware can order this.

You also need to know enough to create your own order, specifying all the materials and dimensions as the roofing is cut to length. Trim comes in standard lengths.

You can find installation guides and other technical specs on the product page.

@PPF Thank you so much!

The Pro Desk at HD can order snap seam roofing. I ordered Fabral brand through them. A full building supply store can order also.

Get cost estimates on each alternative.

.. and don't be surprised at the significant cost difference vs common roofs

Buying the tools and getting familiar with them, plus understsnding all the bits and pieces of the trim, plus the mistakes that ruin material, will take the cost to the stratosphere. It is only worth it for a shed if you are doing a dry run for doing it on a house. The PITA factor is high.

You can buy galvanized rib panel roofing at a big box, these have somewhat of a "standing seam" look - they are flat metal panels with ribs spaced around 12" or so. I built a small shed with this type and it looks great. The sheets are relatively inexpensive and are easily cut with tin snips or a metal cutting blade on a circular saw or jig saw. Closest look to metal standing seam (my house has standing seam). Not the greatest pic but it gives you an idea.