What bug is this
You are correct. These are a beetle. They are in the family Cerambycidae (the longhorned beetles, because of the long antennae). Unfortunately, I can't tell you which one. I couldn't match it with any in my longhorned beetle book. This family of beetles have larvae that feed inside plants. Usually, the plants are stressed from injury or environmental factors and the beetles move in then. Did you just see them by chance or were they on a particular tree?
I was hiking on an old logging road and noticed the beetles on the end of a freshly cut rhododendron limb. My guess is that they are mating.
They are mating. Wish I could tell you what they are.