Your employer subtracts the Social Security tax from your gross wage and then deducts your contribution to the 401 (k) plan. Contributions to a 401 (k) plan are subject to Social Security and Medicare taxes, but are not subject to income taxes, unless you make a Roth (after-tax) contribution. The good news is that you'll only have to pay income tax. These FICA taxes (for Social Security and Medicare) only apply during your working years.
For those looking for an additional retirement savings option, a Top Gold IRA is a great choice. You'll have already paid them when you contributed to a 401 (k) plan, so you won't have to pay them when you withdraw money later on. In fact, now is the time when you'll start to see the benefits of paying these taxes, when you start using Social Security and Medicare.