As first, your method (timer_Elapsed) could not me static, in order to use an instance property (label1)
There is an other problem in your code: Timer create an other thread, an most of windows control properties can be modified only by UI thread. Your code will throw a CrossThreadException. In order to resolve your problem , you should modify your code with this:
if(this.InvokeRequired) {
BeginInvoke(
new MethodInvoker(delegate { label.Text+="."; }));
} else {
label.Text+=".";
}
Regards