Most venues have their own sound system and microphone. If you plan on using it during your event then do yourself a favour and TEST IT! We can not tell you how many times we’ve been to a venue who’s house system sucks!
What does an adequate sound check look like? Don’t just say “testing 1,2,3…” And call it good. Actually stand in the spot where the mic will be used and then talk into it. Listen for any feedback (that high pitched ringing sound which you don’t want). Then have someone else talk into the mic while you walk around the room listening to see how it sounds in different spots in the room, will the people at the back be able to hear? Check to see if it’s loud enough. Remember the room won’t be empty and silent at your event you’ll be competing with a crowd of chatty people.
If the system passes your sound check then great. If it sucks then ask your DJ about using their mic and sound system ahead of time. If you go this route then bare in mind that where the DJ is placed in the room matters. You can’t stick the DJ in the corner of a large room and expect to use his mic for speeches. The people sitting close to the DJ will get blasted with sound while the people in the opposite corner won’t be able to hear well and no one will be happy. Consult with your DJ about the floor plan and where would be the best place to have them setup.