Answer: It's great to hear that you're keeping an eye on the insect activity in your garden, and are aware of the level of damage that can affect the growth and yield of your plants! You are a great example of the Chinese saying that the best fertilizer for the garden is the gardener's footsteps.
If the insects are really tiny and jump away quickly when you approach, they're most likely flea beetles. They're found in most gardens, but really thrive in hot, dry conditions. The word "metallic" makes me think you're dealing with the Japanese Beetle. They're flat and almost round and are beautifully colored (dark brown with metallic rainbow tints in the sun). In large numbers they're VERY destructive to most garden plants.
If you fear that the pests will become a big problem, cover the plants with a fabric row cover placed over hoops. Check under the fabric every couple of days to make sure bugs haven't found a way in. Enjoy those sweet spuds!
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