There are a few types of muscles. The most "important" (termused very loosely here) are the smooth muscles, they control allbodily functions that are automatic (heartbeat, digestion, ext.) ifyou were missing any smooth muscle, you could not survive longerthan 3 weeks (for digestion) 3 minutes (heartbeat).The second type, which I am guessing you mean in the question,is skeletal muscles. If you did not have those muscles, life wouldbe possible, but you would be like a sea sponge, food HAS to cometo you, reproduction would not be possible in the manner that weare used to (it would need to be either asexual, or likeplants).