Although in Android viruses as such, do not exist as in windows, if there are certain threats that can damage our device as invasive advertising that can get into the phone or the famous trojan (which the phone itself detects it), among others. I've never used antivirus and nothing has happened to me, but still, if you feel the need I recommend ESET or AVAST (AVG could also fit), the others are more advertising than anything else.