A detox program most likely won't kick start your metabolism. Many of these programs are low in calories and put you into starvation mode, so technically they're more likely to slow your metabolism down. They're not much good for eliminating toxins either, which is their main selling point. There is really no scientific evidence to back up the claims made by these programs, and the body is pretty efficient at clearing out its own toxins anyway.
There is one thing that detox diets are good for: resetting your taste buds. After a week without added salt, fats, sugar and alcohol you'll probably find you enjoy eating healthy foods more and crave junk foods less. So if you're looking to reduce harmful elements in your diet and kick start your metabolism you might want to focus on whole foods such as fruit, veggies, nuts, legumes and unprocessed grains for a week.
Links to detox articles:SmartShape: Does detox work for weightloss?ABC: Detox kits - do they work?The Guardian UK: Detox remedies are a waste of money, say scientistsSense about Science: Detox press release