The Met with the highest wOBA value this season (who has at least 100 plate appearances), by far, is Yoenis Cespedes. His wOBA is .384, which is at the Great level.
This chart from fangraphs.com shows how to interpret a wOBA value:
The next highest Met is David Wright, but his wOBA is 50 points lower at .344 — just Above Average, and he is likely out for the season. So there's a big difference in offensive value between Cespedes and Wright.
Third on the list, just missing being Above Average by a point is James Loney at .339. Interestedly, the player he replaced, Lucas Duda, has a wOBA of only .309, which is Poor, so the Mets upgraded that position with Loney.
Neil Walker (.326) and Curtis Granderson (.325) are in the Average category.
Asdrubal Cabrera (.315) is Below Average.
Michael Conforto (.308), now back in Triple-A, is in the Poor Category.
All the other Mets with at least 100 PA have a wOBA below .300, which is in the Awful category.
Among the Mets with fewer than 100 PA, Kevin Johnson (43 PA) has a wOBA of .398 (Great) and Juan Lagares (96 PA), currently in rehab in the minors, has a wOBA of .327 (Average).
Unfortunately for the Mets, Cespedes and Wright are the only two players with a wOBA at or above Above Average. But in just 43 PA plates appearances, Johnson has earned the right to start playing every day.