In churches that have no elders, the deacons typically function as elders rather than deacons. This is sometimes called a ‘congregational’ form of church government. In these churches, the congregation typically delegates the leadership of the church to the deacons with pastoral guidance from the senior pastor. In such cases, the congregation is usually asked to vote on more of the decisions of the church. But in reality, the deacons are functioning as elders though they are called deacons.
Then there are those churches governed by a plurality of elders where the deacons function as helpers to the elders. This is sometimes called a ‘Presbyterian’ form of church government. This is more in keeping with the type of structure outlined in the study, A Biblical Philosophy of Ministry on our web site.
Many churches have an elder board consisting of several men, along with a paid pastoral staff. Typically in this situation, it is the pastor (or pastors) who functions as elders, and the elders function more like glorified deacons. I find this less biblical, though it is the norm in the U.S. Biblically speaking, elders are pastors and should be functioning as such—doing the work of shepherding. For many elder boards today, most of their work is administrative and there is often little involvement in the lives of the people as shepherds. Sadly, very few churches really do arrive at a truly biblical balance.
The point, however, is that a plurality of elders should provide the oversight of the church with the deacons serving as their helpers according to the gifts and abilities of the deacons. This could include almost any kind of ministry, but always under the leadership and oversight of the elders.