1. Leadership. Surprise! Of course, you are leading an entire group of musicians, and you need to be able to gather them all together and lead them in the way the music needs to go. So basic leadership skills are quite necessary. In the same manner, you will be leading the congregation through the musical part of the service, so you need to have the kind of presence that keeps people with you.
2. Ability to take direction. Just the opposite of #1, I know. But your job is to enhance the church service through music, and in order to do that, you need to be in tune with what the church leadership wants to do. So you'll need to be able to take direction from the ministers or whomever is in charge of the service.
3. Composition. Many churches create their own original music based on the teachings or spiritual direction of the ministry. Nearly all worship leaders I know are composers. In addition to composition, you may need to lead or guide others on the worship team who are also songwriters, so a knowledge of composition is important.
4. Singing. If you're gonna lead, you've got to be able to sing. And that's gonna mean melody AND harmony. As part of the leadership role, you'll need to direct the other musicians in their parts - especially helping singers find their harmony parts and rehearse them.
That being said, you're going to have difficulty leading worship from behind the drums. That's just a logistical fact. So it may be more appropriate to be a music director WITHOUT being worship leader. Or perhaps for a number of services you do not play drums, and lead worship instead.
Hope that helps.