As a $mtl holder, i saw tweets about it's being delisted on bittrex. And today Bittrex made a warning in Metal trade page:
Metal CEO Marshall Hayner says it's going to be relisted after Pay application release, in spring of 2018:
https://blog.metalpay.com/bittrex-and-metal/
So, people who are interested in this coin should buy it from Binance or somewhere else. I think the Metal Pay project looks interesting and this delisting situation isn't about security or low volume issue.