S., the answer to this question depends on what kind of problems he's having. Does he know his ABCs? Does he understand that the letters mean certain sounds? Where does his trouble seem to lie?
Not all children read by age 7. Some read very early--I read at age 5 or so, and some children don't get the hang of it until they are 8 (second grade). Is your son in school, or are you homeschooling? See if you can talk to a teacher or specialist to find out if he is having some kind of developmental reading problem. Also get his hearing checked because he may not be able to hear certain sounds that these shapes on the paper that we call letters make. There could be any number of reasons why he is having trouble in this area, so get some professional opinions.
But please do not stress out about this. Don't punish him for not catching on or he will HATE reading for his entire life. Make it as fun and enjoyable as you can. Turn reading times into bonding times. Do you read to him? Make it a fun time, a cuddling time.
Remember that all children mature and learn at different rates and in different ways. Look up information on Learning Style Theory. Some children are more physically-oriented, and they need to find physical ways to learn, such as having letters that they can touch and move around. Others are more oriented toward their sense of hearing, and they need to focus on associating the shape of the letter with the sound it makes. Still others are visually-oriented -- they need to associate sound with shape, but in a different way, with lots of colors and so forth.
Making up songs to help children remember the beginning skills of reading is great, because developmentally, we all remember songs easier than speech, and also children who are physically-oriented can add movements and dancing to the song.
Teach to the child's strengths at first, and then when he has gotten a solid mastery, you can work on strengthening his weaknesses so that he can be a more flexible learner.
I hope this is helpful.
Peace,
Syl