discord.py commands won't work even though I am typing them correctly(i think)

async def commands(ctx):
    await bot.say('commands: blah blah blah')

please tell me if this code should work, my bot is able to go online, but the only commands i can make are created using 

if message.content.startswith('.....'):

and its annoying me to not know why the @bot.command commands never work