The current event you choose for this assignment must be one with which you feel a connection and which is suitable for your age/grade, your audience, and your location/geography, since what issues matter to people tend to vary based on these three factors. I can offer you some strategies which can be applied to whatever current events topic you choose.
After choosing your current events topic. determine how you feel about it. Does it make you angry, does it create pity, does it inspire you...you get the idea. Your answer to this question will determine the tone for your writing. Use the kind of language which reflects your emotion. For example, if you are outraged that the local animal shelter will be forced to close its doors because the city refuses to fund the facility any longer, your monologue might contain things like "unthinkable," "tragic loss," "unfair," or "desperate situation."
Once you choose your tone, determine what you want your audience to do with what you tell them. This is your agenda. Using the same pet shelter story as an example, perhaps you want to encourage your audience to take action. If that is so, your language should be clear and persuasive, giving the facts about the closing and what the listeners can do to prevent it if they want to take action.
The interesting thing about current events is that not everyone in the audience is likely to care equally about the same kinds of things, so it is essential that you do your best to make your audience care about the subject. That means you need to present compelling evidence about the subject in a way that connects with the audience. Why, for example, should people who do not even like pets care that the shelter is closing? Perhaps you have data that shows that this closing will mean more stray animals are likely to be seen all over town. Perhaps you need to appeal to a sense of fairness by pointing out that at the same time the city is taking money away from the shelter it is spending money on fancy new signs in the city park. Be intentional about what you share, but keep in mind that you still have to be honest and honorable with your data.
It is important to understand that persuasive writing relies heavily on facts--not opinions.
All the rules of regular writing still apply; your monologue should contain an interesting introduction, some clear and organized points, and an effective conclusion.
Every current event topic does not have to be heavy or depressing or life-and-death. How about looking for something kind of outrageous or even silly that somebody, somewhere thinks is important but is likely to be amusing to your audience. I linked an article below, for example, which addresses a serious problem, traffic accidents caused by deer, with a rather humorous solution--glow-in-the-dark antlers. The tone for this current event might change from serious to humorous or stay humorous throughout. Your choice of language will determine the tone.
Some ideas for current event topics might include things connected to students, such as educational, sports, or teen issues on a local, state, or national level. How budget cuts impact student activities or learning is likely to catch the interest of students. Community or state issues, crises in the entertainment industry, or things from around the world that have a direct connection to your audience would also work well.
Choose something about which you have some passion or interest, and the writing will come easily to you.
You could write your piece on the current state of the Ukraine. They've been in turmoil for a while, and big things have happened recently. You could chose one side, the protestors or the police, and research their position more and find out exactly why they are doing what they are doing.