The metals are all split by two categories. They are either pushing or pulling, and either internal or external. But the number 16, being a power of 2, could be split four times. Is it possible for there to be more categories? the table here just splits this into 4 categories, rather than 2 sets of 2. Is there a common grouping?
Moving on, the same category system, I believe, may apply to the shards. Already, we've seen pairings of shards, like ruin and preservation, and devotion and dominion. Notably, in each pair, there appears to be one "loving" shard, that "Pulls" people together, and one "aloof" shard, that "pushes" people away, or one "good" and one "evil" shard. Endowment would appear to be a "loving", along with cultivation, and honor, while odium, autonomy, and possibly this "Hiding/survival" shard appear to be aloof. Of course, I wouldn't suggest that these are the proper intents of this division. Another way we could try splitting these shards into categories is by the fact that some can see the future and some can't, suggesting another division.
Already, we know that preservation and cultivation are good at foresight, while ruin and honor aren't so good. What other divisions can we glean, and could we use this to predict other shards?
Could "survival" be the counterpart to cultivation?
Could there be a counterpart to "Autonomy", "Society"?
Only Brandon knows.